Anatomy of the Cat

by Jacob Reighard; H. S. Jennings

DIRECTIONS FOR DISSECTING THE MUSCLES OF THE CAT.

I. The Skin-muscles ([pp. 93]-[96], and [Fig. 62]).

These will perhaps not usually be dissected. If they are to be dissected, proceed as follows: Make a ventral median longitudinal incision of the skin from the cranial end of the manubrium to a point opposite the crest of the ilium. Connect the cranial end of this incision with the middle of the lambdoidal ridge by a similar incision through the skin. Make another incision from the manubrium to the spinous process of the thirteenth thoracic vertebra. Connect the caudal end of the first incision by an oblique cut with the root of the tail. Make another incision from the convexity of the knee-joint along the fold of skin which connects the hind limb and body, as far as the incision which leads to the root of the tail. Make an incision surrounding the base of the forelimb. Now reflect these flaps one at a time, working in general from the ventral side toward the dorsal middle line. Take great pains not to take up the thin skin-muscle with the skin. In this way all of one side of the body will be uncovered. The cutaneus maximus ([Fig. 62], b) and a part of the platysma ([Fig. 62], a) will be thus exposed. Read and verify the descriptions of these muscles ([pp. 93]-[96]). The cranial portion of the platysma cannot be seen at this stage, but should be dissected in connection with the muscles of the face.

II. Superficial Muscles of the Face and Head ([pp. 96]-[107], and [Figs. 63] and [64]).

These will perhaps not usually be dissected by the student. They should be studied on a well-dissected laboratory preparation, if possible. If they are to be dissected, this should be done if possible on a fresh specimen, as it is very difficult to dissect them on preserved material. Proceed as follows:

The skin should be removed with care from the sides and top of the face and head, without injury to the external ear.

1. The platysma ([p. 95], and [Fig. 62], a). Determine its cranial attachments.

2. The intermedius scutulorum ([p. 96], and [Fig. 63], a).

3. The corrugator supercilii medialis ([Fig. 63], b).

4. The orbicularis oculi ([Fig. 63], c; [Fig. 64], s).

5. The corrugator supercilii lateralis ([Fig. 64], k).

6. Notice the frontoauricularis if it exists.

7. The levator auris longus ([Fig. 63], g, g′). Transect and reflect.

8. The auricularis superior ([Fig. 63], k). Transect.

9. The abductor auris longus ([Fig. 63], m). Transect.

10. The abductor auris brevis ([Fig. 63], l). Transect.

11. The epicranius ([Fig. 63], h, h′). In dissecting this muscle the intermedius scutulorum and corrugator supercilii medialis may be cut by an incision parallel to the middle line but a short distance to one side of it.

12. The zygomaticus ([Fig. 64], d). This and the two following muscles may usually be best seen running beneath the fibres of the platysma, without reflecting the latter. If necessary, however, the platysma may be transected and reflected, though this can be done only with great difficulty.

13. The submentalis ([Fig. 64], c).

14. The depressor conchæ ([Fig. 64], b).

The zygomaticus, submentalis, and depressor conchæ should now be transected one or two centimeters from the external ear. The corrugatores supercilii lateralis and medialis may be cut across between the eye and the ear, and reflected. There is thus exposed:

15. The frontoscutularis. Transect near the scutiform cartilage.

16. The adductor auris inferior ([Fig. 64], o). Transect near its insertion.

The external ear is now attached to the head only by the external auditory meatus and the tragicus lateralis muscle. Read the description of the latter ([p. 418], and [Fig. 67], a), find it beneath the fat which surrounds the proximal portion of the external ear, and cut it as far ventrad as possible. Now cut across the cartilaginous auditory meatus as near to the tympanic bone as possible, and remove the external ear, preserving it for future study. (The remainder of the muscles of the external ear may be studied in connection with the study of the auditory organ.)

17. The orbicularis oris ([p. 105] and [Fig. 64], i).

18. The zygomaticus minor, if it exists ([p. 105], and [Fig. 64], e).

19. The quadratus labii superioris ([p. 105]).

a. The levator labii superioris proprius ([Fig. 64], f).

b. The levator labii superioris alæque nasi ([Fig. 64], g).

20. The caninus ([p. 106], and [Fig. 64], f′).

21. The buccinator ([p. 106]).

22. The myrtiformis ([p. 106], and [Fig. 64], h).

23. The “moustachier” ([p. 107]).

24. The quadratus labii inferioris ([p. 107]).

III. Muscles of the Fore Limb.

A. Muscles connecting the Arm with the Body.

—If the skin-muscles have been dissected, as above, cut the cutaneus maximus near its insertion, and reflect it toward the median dorsal line; in this way remove it completely. Remove the platysma in the same way. The first layer of body-muscles is thus exposed.

If the skin-muscles are not to be dissected, these may be removed with the skin. If the skin has not yet been removed, proceed as follows:

Beginning at the cranial end of the manubrium make two incisions in the skin, one passing to the lambdoidal ridge and the other to the spinous process of the thirteenth thoracic vertebra. Raise the triangular flap thus formed, taking up the skin-muscles with it.

1. The trapezius group of muscles ([pp. 115]-[117], and [Fig. 68], d, h, and j) is now exposed and may be dissected. Begin with the spinotrapezius ([Fig. 68], j). Read the description of the muscle, then raise its caudal border and work under it until its cranial border is reached and the middle of its inner surface is free. Then transect it, and reflect the two halves of the muscle toward the origin and insertion, clearing the fat, etc., from the inner surface of the muscle and the parts covered by it. Determine origin and insertion.

2. The acromiotrapezius ([Fig. 68], h). Dissect in the same manner, being careful not to injure the broad thin tendon which connects the two muscles across the middle line.

3. The clavotrapezius ([Fig. 68], d). Separate it carefully, from the cleidomastoid ([p. 120]). Transect and reflect, as before.

4. The occipitoscapularis ([Fig. 73], a, [p. 149]). Note the strong fascia which separates it from the deeper muscles of the neck. Be careful not to injure adjacent muscles in tracing this toward origin and insertion. Transect.

5. The rhomboideus. Transect.

Recognize the levator scapulæ ventralis ([Fig. 68], f), the sternomastoid ([Fig. 68], c; [Fig. 65], g), and the cleidomastoid ([Fig. 65], h). Then dissect—

6. The levator scapulæ ventralis ([Fig. 68], f). Its origin ([Fig. 72], c, c′) cannot be seen at this stage and should be left until the cervical muscles are dissected. Be careful in transecting this muscle to separate it well from the cleidomastoid. Transect.

7. The cleidomastoid ([Fig. 65], h). Its origin cannot be fully seen at this stage. Transect.

Make a midventral incision of the skin from the cranial end of the manubrium to a point opposite the crest of the ilium. From the caudal end of this incision make an incision to the root of the tail. From the cranial end of the incision in the ventral middle line make a cut around the base of the fore limb on its caudal side, thus connecting the ventral incision with the incision which passes between the manubrium and the thirteenth thoracic vertebra.

Make another incision from the convexity of the knee at the joint along the fold of the skin which connects the hind limb and body, to the incision which leads to the root of the tail.

Reflect the flaps thus formed so as to expose the body and flank, removing the skin-muscle with the skin.

8. The latissimus dorsi ([p. 121], and [Fig. 68], m). Dissect it up and transect it. Work carefully toward its insertion and note the origin from its outer surface in the axilla of a part of the cutaneus maximus, and at about the same place of a thin muscle, the epitrochlearis ([p. 164], and [Fig. 65], r), without determining the insertion of the latissimus.

9. Dissect the pectoralis group of muscles ([Fig. 65], and [p. 144]), i.e., the pectoantibrachialis ([Fig. 65], m), the pectoralis major (l), pectoralis minor (o), and xiphihumeralis (p).

Determine the border of each muscle before lifting it, then work it up at its middle, transect it, and work toward its ends, determining origin and insertion.

Refer constantly to the skeleton.

10. Then recognize the teres major ([p. 163], and [Fig. 75], d; [Fig. 77], c) and the common insertion of the teres major and latissimus ([Fig. 79], d′); find the bicipital arch ([Fig. 65], t′) and determine its composition ([p. 166]).

11 and 12. The serratus anterior and levator scapulæ ([Fig. 73], h and i, and [p. 122]). In order to expose the origin of these muscles, the external oblique muscle ([Fig. 68], p) must be recognized, and that part of it which has its origin from the fourth to the ninth rib should be transected about an inch and a half from its origin and reflected.

The thoracic portion of the rectus abdominis ([Fig. 73], k) and of the scalenus ([Fig. 73], f-f‴) should also be recognized and then raised at their outer borders and displaced toward the median line. No part of any of these muscles should be removed or cut except as directed.

The serratus anterior and levator scapulæ should be transected and reflected to get at their origin and insertion.

B. Muscles of the Arm

([p. 156]).—The arm is thus removed from the body and the dissection may be continued on the separated arm.

13. The clavobrachial ([Fig. 65], k, and [p. 157]). Its origin is best seen later. Dissect it up, but do not transect it.

Search now with great care for the coracobrachialis. Consult the figures ([Fig. 79], c) and descriptions ([p. 164]), and be especially careful not to injure the long head of the muscle and its tendon.

14. Dissect the coracobrachialis ([Fig. 77], f). Cut and reflect it.

15. The subscapularis ([Fig. 77], a, and [p. 161]). Near its glenoid end, its glenoid and coracoid borders are separated by triangular intervals from the adjacent muscles. Transect the muscle by a line connecting the apices of these triangles. Carry an incision from the middle of this one to the middle of the vertebral border of the scapula, and reflect the muscle on both sides of this incision,—thus determining its area of origin. Reflect the humeral end without injuring the capsule of the joint.

16. Dissect the supraspinatus ([Fig. 75], a, and [p. 159]). Cut the strong fascia free from the border of the scapula and its spine. Then transect the muscle and reflect it, being careful not to injure the capsule of the joint.

17. The spinodeltoideus ([Fig. 75], e, and [p. 156]). Find its two borders, beginning with the caudal one. In freeing the very short cranial border do not injure the acromiodeltoideus ([Fig. 75], f). Transect and reflect the spinodeltoid.

18. The acromiodeltoideus ([p. 157], and [Fig. 75], f). Transect and reflect.

19. The infraspinatus ([p. 160], and [Fig. 75], c). Locate the borders in the region of the great scapular notch. It is difficult to separate the glenoid border from the adjacent teres minor ([Fig. 80], c). The separation should be begun at the humerus. Transect the muscle at the great scapular notch and reflect. Be careful not to injure the teres minor ([Fig. 80], c).

20. The teres major ([p. 163], and [Fig. 75], d; [Fig. 77], c) should be cut near its junction with the latissimus dorsi ([Fig. 77], e).

21. The teres minor ([Fig. 80], c, and [p. 161]) need not be cut.

22. The epitrochlearis ([p. 164], and [Fig. 65], r).

23. The triceps ([p. 166]). (a) The long head of the triceps ([Fig. 77], i; [Fig. 75], g). Find first its medial border and separate it from the medial head. Note the union of its lateral surface with the dorsal border of the lateral head by strong fascia, and then cut the fascia.

(b) The lateral head ([Fig. 75], h).

(c) The medial head ([Fig. 79], g, h, and j).

24. The anconeus ([p. 170], and [Fig. 80], l).

25. The brachioradialis ([p. 173], and [Fig. 75], k). Reflect it carefully to its origin and insertion.

26. The biceps ([Fig. 77], g, and [p. 165]). The capsule of the shoulder-joint may be opened in order to expose its origin. Its insertion cannot be seen at this stage.

27. The brachialis ([Figs. 75] and [79], i, and [p. 166]). Work under it near its union with the clavobrachial; cut it at that point and reflect it.

28. Extensor carpi radialis longus ([p. 173], and [Fig. 75], l). Note the oblique tendon on the radial side of the wrist near the insertion of the brachioradialis. A second tendon passes beneath its distal border. This tendon may be separated into a deep and superficial portion. The latter may be traced proximad to its muscle, the extensor carpi radialis longus.

29. Extensor carpi radialis brevis ([p. 174]). Its tendon is the deeper of the two tendons seen when isolating the tendon of the extensor longus.

30. Extensor communis digitorum ([p. 174], and [Fig. 75], m).

31. Extensor lateralis digitorum ([p. 175], and [Fig. 75], n).

32. Extensor carpi ulnaris ([p. 176], and [Fig. 75], o).

33. Extensor indicis ([p. 176], and [Fig. 85], c).

34. Pronator teres ([p. 179], and [Fig. 77], q).

35. Flexor carpi radialis ([p. 179], and [Fig. 77], r). The tendon of the flexor carpi radialis should not be traced to its insertion until the deep muscles of the palm of the hand have been dissected.

36. Abductor brevis pollicis ([p. 184], and [Fig. 77], w).

37. Flexor carpi ulnaris ([p. 180], and [Fig. 77], t).

38. Palmaris longus ([p. 179], and [Fig. 77], s). In dissecting this muscle be careful not to injure the part of the flexor sublimis ([Fig. 77], x) that rises from its surface (see flexor sublimis, [p. 181]). Cut the palmaris proximad of the origin of the flexor sublimis and reflect it.

39. Flexor sublimis digitorum ([p. 181] and [Fig. 77], x). Trace one or two of the tendons through the sheaths on the ventral surfaces of the first phalanges. Cut and reflect the radial portion.

40. Flexor profundus digitorum ([p. 181], and [Fig. 77], u). After recognizing the parts cut through the tendons of the first and fifth parts and reflect them to determine their origin. Then cut through the common tendon so as to reflect the other three parts together. Trace one or two of the tendons to the distal end of the digit.

41. The supinator ([p. 177], and [Fig. 85], b).

42. The extensor brevis pollicis ([p. 178], and [Fig. 85], a).

43. Pronator quadratus ([p. 183], and [Fig. 87], a).

The insertion of the brachialis and clavobrachial ([Fig. 87], c) and of the biceps ([Fig. 87], b) should now be examined.

There remain to be dissected the small muscles of the palm of the hand. If these have been injured on the side dissected, the hand of the other side may be used.

44. The lumbricals ([p. 184], and [Fig. 88], f).

45. The flexor brevis pollicis ([p. 184], and [Fig. 89], a).

46. The adductor pollicis ([p. 185], and [Fig. 89], b).

47. The abductor digiti quinti ([p. 185], and [Fig. 89], i).

48. The flexor brevis digiti quinti ([p. 186], and [Fig. 89], h). Cut and reflect it.

49. The opponens digiti quinti ([p. 186], and [Fig. 89], g). Cut and reflect it.

50. The interossei ([p. 185], and [Fig. 89]).

IV. Muscles of the Neck and the Deep Muscles of the Head.

If the superficial muscles of the head have been dissected according to the directions above given ([p. 434]), the skin of the head and neck, and the external ear, will have been removed, and the specimen is ready for further study. The parotid and submaxillary glands ([Fig. 65], 1 and 2) should be removed if this has not been done; also the lymphatic glands ([Fig. 65], 3).

If the superficial muscles of the head have not been dissected and are not to be, remove the skin from the side of the neck, head, and face to the median dorsal line, removing the thin superficial muscles with the skin. Remove also the parotid, submaxillary, and lymphatic glands ([Fig. 65], 1, 2, and 3), and cut through the ear-muscles and the cartilaginous auditory meatus (under direction) and remove the external ear. Clean fat, connective tissue, etc., from the surface of the muscles of the thorax, neck, and head; then dissect as follows:

1. The sternomastoid ([p. 139], and [Fig. 65], g). Transect and reflect it.

2. The cleidomastoid ([p. 120], and [Fig. 65], h). This has already been transected; examine now its origin.

Remove the large lymphatic gland beneath the sternomastoid and close to the tympanic bulla, and clean the surface of the muscles in this region.

3. The levator scapulæ ventralis ([p. 120], and [Fig. 72], c, c′, c″). This has already been cut; study now its origin.

4. The sternohyoid ([p. 140], and [Fig. 65], e). In raising it begin at the cranial end and take care not to injure the subjacent sternothyroid ([Fig. 65], g′). Transect.

5. The sternothyroid ([p. 141], and [Fig. 65], g′). Transect.

6. The stylohyoid ([p. 112], and [Fig. 65], d). Transect.

7. The digastric ([p. 107], and [Fig. 65], b). Transect, and reflect completely, to the origin and insertion.

8. The mylohyoid ([p. 114], and [Fig. 65], c). Transect and reflect.

9. The geniohyoid ([p. 113], and [Fig. 67], g).

10. The jugulohyoid ([p. 113], and [Fig. 67], b).

(The extrinsic muscles of the tongue ([p. 228], and [Figs. 67] and [96]) may be dissected at this point, if desired. (a) The styloglossus; (b) the genioglossus; (c) the hyoglossus. They need not be cut.)

11. The masseter ([p. 108], and [Fig. 65], a). Cut the superficial and middle layers near their insertions by incisions parallel to the border of the jaw. Cut the deep layer near its origin. Look for the origin of fibres of the temporal muscle from the inner surface of the middle layer.

12. The temporal ([p. 110], and [Fig. 63], n). Clear its outer surface completely. Cut the temporal fascia transversely and reflect it toward the insertion of the muscle, with the superficial portion of the muscle. Cut through the zygomatic arch at its two ends and remove it, dissecting the fibres of the temporal free from their origin on its inner surface. Then examine the insertion of the temporal.

(The muscles of the pharynx ([p. 232]) may be dissected at this point; for directions, see [page 451].)

13. The ceratohyoid ([p. 115]). To uncover this, the middle constrictor of the pharynx ([Fig. 67], j) must be cut and reflected.

Cut the mylohyoid, geniohyoid, genioglossus, and the mucosa of the floor of the mouth free from the mandible on both sides, so that the tongue and the floor of the mouth may be drawn ventrad and turned out of the way, exposing the roof of the mouth (as in [Fig. 66], [p. 112]). Cut through one side of the pharynx near the ventral surface and turn the tongue toward the uncut side.

The roof of the mouth is thus exposed. Dissect next—

14. The pterygoid muscles ([Fig. 66]). Remove the mucosa of the roof of the mouth, especially at the sides of the soft palate, and the two pterygoid muscles ([p. 111]) are exposed. The lower jaw may be removed on one side to get at their origin.

(The muscles of the soft palate ([p. 230], and [Fig. 66], d and e), and the superior constrictor of the pharynx ([p. 233], and [Fig. 66], f) may be observed at this point, if desired.)

V. Muscles of the Wall of the Thorax and of the Abdomen.

1. The scalenus ([p. 141], and [Fig. 73], f-f‴). To trace its cervical portion, cut the trachea and œsophagus just craniad of the first rib, cut the pharynx and hyoid free from the ventral side of the head and neck, and remove the pharynx, larynx, œsophagus, and trachea (these should be preserved for future study of the larynx).

2. The transversus costarum ([p. 150], and [Fig. 73], j).

3. The serratus posterior superior ([p. 148], and [Fig. 73], l). Transect this at about the middle of the muscle-bundles, and reflect it in both directions.

4. The serratus posterior inferior ([p. 148], and [Fig. 73], n). Transect and reflect as in the last.

5. The external oblique ([p. 153], and [Fig. 68], p). Transect it by an incision parallel to its tendon of origin and about an inch from it, and reflect in both directions.

6. The internal oblique ([p. 154], and [Fig. 73], o). Transect and reflect as above.

7. The transversus ([p. 155], and [Fig. 69], l). Requires no further dissection.

8. The rectus abdominis ([p. 155], and [Fig. 73], k). Open its sheath by a longitudinal incision near the linea alba.

9. The external intercostals ([p. 150], and [Fig. 73], m; [Fig. 69], i). To see these, remove the origins of the levator scapulæ and serratus anterior; also the serratus posterior superior.

10. The internal intercostals ([p. 151], and [Fig. 69], k). To uncover these, remove the external intercostals from between two or three pairs of ribs.

11. The transversus thoracis ([p. 151]). To see this muscle, which lies on the inner surface of the thoracic wall, it is necessary to cut through the ribs on one side one or two inches from the sternum, and open the thorax. The muscle can then be observed directly.

(The levatores costarum will be dissected later.)

VI. Muscles on the Ventral Side of the Vertebral Column in the Neck Region ([Fig. 72]).

Clean the surface of these muscles, removing pharynx, larynx, œsophagus, and trachea, if this has not been done.

1. Longus capitis ([p. 142], and [Fig. 72], a).

2. Longus colli ([p. 144], and [Fig. 72], g′, g″).

3. Levator scapulæ ventralis ([p. 120], and [Fig. 72], c′, c″). Observe its origin.

4. Rectus capitis anterior minor ([p. 143], and [Fig. 72], b). To see this, cut through on one side the longus capitis and one head of the levator scapulæ ventralis, and remove the proximal portions, as in [Fig. 72].

5. Obliquus capitis superior ([p. 136], and [Fig. 72], e).

6. Rectus capitis lateralis ([p. 143], and [Fig. 72], d).

VII. Muscles of the Back ([p. 123]).

Remove what remains of the dorsal portion of the latissimus dorsi, serratus posterior superior, and serratus posterior inferior. See that the skin is removed completely to the dorsal middle line, or even for a little distance over onto the other side. There is thus exposed the lumbodorsal fascia ([p. 126]), covering the muscles of the back.

Cut the superficial layer of the lumbodorsal fascia (that from which the latissimus dorsi and obliquus externus abdominis have origin) by an incision parallel to the dorsal median line, and remove it. The muscles of the back are thus exposed ([Fig. 69]). Observe in the lumbar region the longissimus dorsi (f, f′, f″); in the thoracic region the longissimus dorsi, the spinalis dorsi (g), and the iliocostal (h); in the cervical region the splenius ([Fig. 73], b).

1. The longissimus dorsi ([p. 126], and [Fig. 69], f, f′, f″). Notice in the lumbar region the strong deep layer of the lumbodorsal fascia, by which this muscle is covered, and from the under side of which many of the fibres of the muscle take origin. Cut this fascia by an incision parallel to the dorsal median line and about two centimeters from it, from the level of the crest of the ilium as far craniad as the fascia can be cut without cutting into the muscle-fibres (usually to about the level of the last rib). Reflect the medial division of the fascia to the middle line. Reflect the lateral division of the fascia until it passes into the muscle and cannot be farther reflected.

Observe then in the lumbar region the medial ([Fig. 70], a) and lateral ([Fig. 70], b) divisions of the longissimus dorsi, and the portion (b′) of the lateral division taking origin from the lumbodorsal fascia (c). Dissect apart some of the muscle-fibres of the longissimus and observe their origin and insertion.

Trace the longissimus dorsi into the thoracic and cervical regions ([Fig. 69], f′, f″) noting the separation off from it on the dorsal side of the spinalis dorsi ([Fig. 69], g); on the ventral side of the iliocostal ([Fig. 69], h).

2. The extensor caudæ lateralis ([p. 137], and [Fig. 70], f). Uncover this by cutting the lumbodorsal fascia over the sacral region.

3. The iliocostalis ([p. 128], and [Fig. 69], h). Uncover this completely; note its connection with the longissimus dorsi at the caudal end. Dissect apart some of its muscle-bundles, to see origin and insertion.

4. The splenius ([p. 131], and [Fig. 73], b). Transect this by an incision beginning at its lateral border about four centimeters from the cranial end of the muscle and extending obliquely craniodorsad to the craniomedial angle of the muscle. Be careful not to injure the longissimus capitis ([Fig. 73], g).

5. The longissimus capitis ([p. 131], and [Fig. 73], g). Transect.

6. The spinalis dorsi ([p. 129], and [Fig. 69], g). Separate some of its muscle-fibre bundles and trace to origin and insertion.

7. The biventer cervicis ([p. 132], and [Fig. 69], a). Raise its lateral border, turning it toward the middle line, and transect it near its caudal end.

8. The complexus ([p. 133], and [Fig. 69], b). Raise its medial border, and transect it near its cranial end.

9. The longus atlantis ([p. 134], and [Fig. 71], f).

10. The multifidus spinæ ([p. 130], and [Fig. 70], d). Remove a part of the longissimus dorsi in the lumbar region, and trace the course of the fibres of the multifidus spinæ. (If desired the entire longissimus may be removed and the multifidus spinæ completely uncovered.)

11. The extensor caudæ medialis ([p. 136], and [Fig. 70], e).

12. The semispinalis cervicis ([p. 133], and [Fig. 71], c). Dissect apart some of its fibre-bundles to see origin and insertion.

13. The interspinales and intertransversarii ([p. 131]) may be seen in the region from which the longissimus dorsi was removed, by removing the bundles of the multifidus spinæ.

14. The rectus capitis posterior major ([p. 134], and [Fig. 71], a). Transect.

15. The obliquus superior ([p. 136], and [Fig. 71], e).

16. The obliquus capitis inferior ([p. 136], and [Fig. 71], b).

17. The rectus capitis posterior medius ([p. 135]). Transect.

18. The rectus capitis posterior minor ([p. 135]).

19. The levatores costarum ([p. 150]). Remove in a part of the thoracic region a portion of the iliocostal and longissimus dorsi, so as to expose the dorsal ends of the ribs. The levatores costarum will be seen as but slightly separated bundles continuous with the external intercostals.

VIII. Muscles of the Hind Limbs ([p. 186]).

Remove the skin and superficial fascia from the lateral surface of the thigh. Examine the fascia lata ([p. 186], and [Fig. 68], z). Dissect:

1. The biceps femoris ([p. 194], and [Fig. 68], t). Work under its cranial and caudal borders. Find the tenuissimus ([Fig. 90], g) passing obliquely beneath it and reaching its caudal border in its distal half. Transect the biceps without injuring the tenuissimus, and reflect its halves.

2. The tenuissimus ([p. 195], and [Fig. 90], g). Transect.

3. The caudofemoralis ([p. 195], and [Fig. 68], s). Transect.

4. The gluteus maximus ([p. 187]). Transect.

5. The sartorius ([p. 197], and [Fig. 68], q; [Fig. 91], a). Transect.

6. The tensor fasciæ latæ ([p. 187], and [Fig. 68], r). Cut the fascia lata along the distal end of the muscle-fibres and reflect the muscle.

7. The gluteus medius ([p. 188], and [Fig. 90], b). Work under it carefully, separating it from underlying muscles; cut it close to its tendon of insertion, and reflect it.

8. The pyriformis ([p. 188], and [Fig. 163], 7, [p. 401]). Cut and reflect it.

9. The gemellus superior ([p. 189], and [Fig. 163], 6). This and the next muscle will sometimes be found to be completely united. Transect.

10. The gluteus minimus ([p. 189], and [Fig. 163], 5). Transect.

11. The obturator internus ([p. 192], and [Fig. 90], e). Cut it at the dorsal border of the ischium in order to reflect it. The whole origin cannot be seen at this stage.

12. The gemellus inferior ([p. 190]).

13. The gracilis ([p. 198], and [Fig. 91], b). Transect.

14. The semitendinosus ([p. 196], and [Figs. 90] and [91], j; [Fig. 92], i). Transect.

15. The semimembranosus ([p. 196], and [Figs. 90] and [91], i; [Fig. 92], h, h′). Transect.

16. The adductor femoris ([p. 198], and [Figs. 90] and [91], h; [Fig. 92], g). Transect.

17. The quadratus femoris ([p. 191], and [Fig. 90], f). Transect.

18. The obturator externus ([p. 191]).

19. The adductor longus ([p. 199], and [Fig. 92], f). This and the following will sometimes be found to be almost completely united. Transect.

20. The pectineus ([p. 200], and [Fig. 92], e). Transect.

21. The iliopsoas ([p. 193], and [Fig. 91], c; [Fig. 92], d). Only its distal part, near the insertion, can be seen at present.

22. The capsularis ([p. 190]). Transect.

23. The quadriceps femoris ([p. 201]). Isolate the rectus femoris ([Fig. 92], b) as far as its junction with the vastus lateralis; cut it at this point and reflect its proximal portion. Turn aside the distal end and find beneath it the transverse aponeurosis between the vastus medialis and the vastus lateralis, and covering the vastus intermedius. The vastus lateralis ([Fig. 90], d) may be cut near the middle and dissected up from its origin in both directions; the vastus intermedius is thus exposed. The vastus medialis ([Fig. 92], c) and the vastus intermedius need not be cut.

24. The gastrocnemius ([p. 203], and [Fig. 90], m; [Fig. 91], k). It may be raised cautiously near its middle and divided. Care should be taken not to divide the underlying plantaris ([Fig. 90], l). After noting the connection of the outer head with the plantaris, the latter may be divided and reflected, together with the outer head.

25. The plantaris ([p. 205], and [Figs. 90] and [91], l).

26. The flexor brevis digitorum ([p. 212]). In tracing its tendon note the three branches of the common plantar ligament which emerges from between the second and third tendons. The outer branch is inserted into the fascia covering the base of the fifth digit, while the other two spread out into the bilobed pad of the sole.

27. The soleus ([p. 205], and [Fig. 90], o). Cut and reflect.

28. The popliteus ([p. 206], and [Fig. 92], k). Cut very near the origin and reflect.

The three following deep muscles on the ventral surface of the shank are covered by the deep crural fascia ([p. 206]) which separates them from the overlying muscles. It should be removed.

29. The flexor longus hallucis ([p. 207], and [Fig. 91], m). Divide the muscle at its junction with the tendon. Open the canals on the astragalus and calcaneus and reflect the tendon, cutting the tendon of the flexor longus digitorum near its insertion and dividing at the middle the quadratus plantæ ([p. 213]) which may be found inserted into its ventral surface.

30. Flexor longus digitorum ([p. 208], and [Fig. 91], n). This may be divided very near its origin.

31. Tibialis posterior ([p. 208], and [Fig. 91], o). This may be divided near its tendon.

32. Peroneus longus ([p. 209], and [Fig. 90], q). The overlying tendons may be cut in tracing its insertion.

33. Peroneus brevis ([p. 210], and [Fig. 90], s).

34. Peroneus tertius ([p. 210], and [Fig. 90], r).

35. Extensor longus digitorum ([p. 210], and [Fig. 90], p).

36. Tibialis anterior ([p. 211], and [Fig. 90], n).

37. The extensor brevis digitorum ([p. 212], and [Fig. 90], u).

38. The quadratus plantæ ([p. 213]). It was cut in dissecting the flexor longus hallucis.

39. The lumbricales ([p. 213]).

40. The interossei (with the muscles of the fifth digit) ([p. 214]).

41. The tarsal muscles ([p. 215]). The overlying ligaments must be removed in order to expose the scaphocuneiform.

IX. The Diaphragm and the Muscles on the Ventral Side of the Vertebral Column in the Lumbar and Pelvic Regions.

Remove the ventral and lateral walls of the thorax completely, as far back as the diaphragm,—leaving only a ring attached to the margin of the diaphragm. Remove the abdominal walls in the same way, as far back as the pubis, leaving the diaphragm in position. Remove the thoracic viscera (the heart and lungs may be preserved for future study). Remove also the abdominal viscera as far back as the beginning of the pelvis, cutting the large intestine where it passes into the pelvis. The dorsal wall of the abdominal cavity should be cleared of fat, blood-vessels, etc., without injury to the crura of the diaphragm.

1. The diaphragm ([p. 151], and [Fig. 74]). Study by transmitted light, to see the tendons, etc.

2. The psoas minor ([p. 139], and [Fig. 162], 9, [p. 398]). Find its tendon and separate it from the iliopsoas ([Fig. 162], 8) as far craniad as this can be done without tearing the fibres.

3. The iliopsoas ([p. 193], and [Fig. 162], 8). Find both portions; isolate them as far as it can be done.

4. The quadratus lumborum ([p. 139]). Free the lateral edge of the iliopsoas from the abdominal wall and turn the whole muscle mediad as far as possible. The bundles of the quadratus lumborum will be found beneath it, against the transverse processes of the lumbar vertebræ.

With a heavy cartilage-knife separate the two innominate bones along the pelvic symphysis. This is easily done if the knife is inserted exactly into the line of junction of the two bones. Divaricate the edges some distance, so as to make a ventral opening into the pelvic cavity. If necessary, part of the innominate bone of one side may be removed to make the opening larger.

Find the thin sheet of fibres forming the levator ani muscle ([Fig. 162], 11) at the side of the rectum, attached to the edge of the symphysis. Carefully free the rectum and urogenital organs from this and remove them as far as the anus, leaving the levator ani intact.

5. The iliocaudalis ([p. 137], and [Fig. 162], 11′).

6. The levator ani ([p. 269], and [Fig. 162], 11).

Remove with great care the levator ani and iliocaudalis of one side, by cutting first the attachment to the symphysis and the ilium, turning the muscle mediad, then cutting the attachment to the tail. There are thus exposed on the lateral wall of the thorax the medial surface of the obturator internus, craniad of it the pyriformis, caudad of it the quadratus femoris. Dorsad of these is the abductor caudæ internus.

7. The abductor caudæ internus ([p. 137]).

On the ventral surface of the tail are exposed the following:

8. The flexor caudæ longus ([p. 138], and [Fig. 162], 12).

9. The flexor caudæ brevis ([p. 138], and [Fig. 162], 13).

X. Muscles of the Tail ([p. 136]).

By removing the skin of the tail, all the muscles of the tail are now easily seen.

1, 2, 3, 4, 5—see [5, 6, 7, 8, 9], above (IX).

6. The abductor caudæ externus ([p. 137], and [Fig. 113], b; [Fig. 70], g).

7. The extensor caudæ lateralis ([p. 137], and [Fig. 70], f).

8. The extensor caudæ medialis ([p. 136], and [Fig. 70], e).