In some cases the dissection of the calf is the only feasible means of delivering it through the natural passages; and while it is especially applicable to the dead calf, it is also on occasion called for in the case of the living. As a rule, the living calf should be preserved, if possible, but if this threatens to entail the death of the cow it is only in the case of offspring of rare value that its preservation is to be preferred. To those acquainted with the toil, fatigue, and discomfort of embryotomy, no discussion is necessary so long as there is a prospect of success from the simple and generally easier method of rectifying the faulty position of the calf. When the correction of the position is manifestly impossible, however, when distortions and monstrosities of the fetus successfully obstruct delivery, when the pelvic passages are seriously contracted by fractures and bony growths, when the passages are virtually almost closed by swelling, or when the calf is dead and excessively swollen, no other resort may be available. In many cases of distortion and displacement the dismemberment of the entire calf is unnecessary, the removal of the offending member being all that is required. It will be convenient, therefore, to describe the various suboperations one by one and in the order in which they are usually demanded.
Amputation of the fore limb.—In cutting off a fore limb it is the one presenting that should be selected, since it is much more easily operated on, and its complete removal from the side of the chest affords so much more space for manipulation that it often makes it easy to bring the other missing limb or the head into position. The first consideration is to skin the limb from the fetlock up and leave the skin attached to the body. The reasons for this are: (a) That the skin is the most resistant structure of the limb, and when it has been removed the entire limb can be easily detached; (b) the tough skin left from the amputated limb may be used as a cord in subsequent traction on the body of the calf; (c) the dissection and separation of the limb are far more safely accomplished under the protection of the enveloping skin than if the operator's hands and instruments were in direct contact with the walls of the passages or womb; (d) the dissection can be much more easily effected while the skin is stretched by the left hand, so as to form a comparatively firmer resistant point for the knife, than when it is attempted to cut the soft, yielding, and elastic tissues which naturally offer little solid resistance, but constantly recede before the cutting edge of the instrument. The preservation of the skin is therefore a cardinal principle in the amputation of all parts in which it is at all feasible.
The presenting foot is inclosed in a noose and drawn well out of the passages. Then a circular incision through the skin is made around the limb just above the fetlock. From this the skin is slit up on the inner side of the limb to the breast. Then the projecting part of the limb is skinned up to the vulva, traction being made on the foot by an assistant so as to expose as much as possible. The embryotomy knife may now be taken ([Pl. XXI], fig. 2), and a small hole having been cut in the free end of the detached portion of skin, that is seized by the left hand and extended while its firm connections with the deeper structures are cut through. The looser connections can be more quickly torn through with the closed fist or the tips of the four fingers held firmly together in a line or with the spud, of which there are several kinds. Much of the upper part of the limb can be skinned more speedily without the knife, but that must be resorted to to cut across tough bands whenever these interrupt the progress. The skinning should be carried upward on the outer side of the shoulder blade to the spine or nearly so. Then with the knife the muscles attaching the elbow and shoulder to the breastbone are cut across, together with those on the inner side of the shoulder joint and in front and behind it as far as these can be reached. Steady traction is now made upon the foot, the remaining muscles attaching the shoulder blade to the trunk are torn through with a cracking noise, and the whole limb, including the shoulder blade and its investing muscles, comes away. If the shoulder blade is left the bulk of the chest is not diminished, and nothing has been gained. Before going further it is well to see whether the great additional space thus secured in the passages will allow of the missing limb or head to be brought into position. If not, the other presenting part, limb or head, is to be amputated and extracted. For the limb the procedure is a repetition of that just described.
Amputation of the head.—The head is first seized and drawn well forward, or even outside the vulva, by a rope with a running noose placed around the lower jaw just behind the incisor teeth, by a sharp hook inserted in the arch of the lower jaw behind the union of its two branches and back of the incisor teeth, or by hooks inserted in the orbits, or, finally, in case the whole head protrudes, by a halter. ([Pl. XXI], figs 4a and 4b.) In case the whole head protrudes, a circular incision through the skin is made just back of the ear, and the cut edge being held firmly by the left hand, the neck is skinned as far as it can be reached. Then the great ligamentous cord above the spine is cut across at the farthest available point, together with the muscles above and below the spine. Strong traction on the head will then detach it at this point and bring it away, but should there still be too much resistance the knife is inserted between the bodies of two vertebræ just behind one of the prominent points felt in the median line below, and their connecting fibrous cartilage is cut through, after which comparatively moderate pulling will bring it away. The detached neck and body at once slip back into the womb, and if the fore limbs are now brought up and pulled they are advanced so far upon the chest that the transverse diameter of that is greatly diminished and delivery correspondingly facilitated.
If the head is still inclosed in the vagina two methods are available: (1) The removal of the lower jaw and subsequent separation of the head from the neck; (2) the skinning of the whole head and its separation from the neck.
To remove the lower jaw the skin is dissected away from it until the throat is reached. Then the muscles of the cheeks and side of the jaw (masseters) are cut through and those connecting the jaw with the neck. When traction is made on the rope around the lower jaw it will usually come away with little trouble. Should it resist, its posterior extremity on each side (behind the grinding teeth) may be cut through with bone forceps or with a guarded bone chisel. ([Pl. XX], fig. 8.) After the removal of the lower jaw the way will be open to separate the head from the neck, the knife being used to cut into the first or second joint from below, or the bone forceps or chisel being employed to cut through the bones of the neck. Then traction is made on the head by means of hooks in the orbits, and the hand, armed with an embryotomy knife, is introduced to cut through the tense resisting ligament, and muscles above the bones. The skin and the strong ligamentous cord attached to the poll are the essential things to cut, as the muscles can easily be torn across. Unless there are great difficulties in the way it is well to skin the head from the eyes back, and on reaching the poll to cut through the ligament and then bring the head away by pulling.
If it is decided to remove the entire head at once, it may be skinned from the front of the eyes back to behind the lower jaw below and the poll above, then cut through the muscles and ligaments around the first joint and pull the head away, assisting, if need be, in the separation of the head by using the knife on the ligament of the joint.
If the calf is a double-headed monster, the skinning of the head must be carried backward until the point has been reached where both heads branch from the single neck, and the separation must be made at that point. The muscles and ligaments are first to be cut through; and if the part can not then be detached by pulling, the bodies of the vertebræ may be separated by passing the knife through the joint. The second head may now be secured by a noose around the lower jaw or hooks in the orbits and brought up into place, the body being pushed back toward the other side by a repeller, so as to make room.
It should be added that, except in the case of a double-headed monster, or in case of the head protruding or nearly so, and one or both fore limbs presenting, it is rarely desirable to undertake amputation of the head. The space desirable in the passages can usually be obtained by the much simpler and easier procedure of removing one or both fore limbs.