What causes the hollow eye and sunken cheek after a severe sickness? 158. How many muscles in the human system? Into how many layers are they arranged? What is a voluntary muscle? Give examples. What is an involuntary muscle? Mention examples. Give observation 1st, respecting the use of the abdominal muscles? Observation 2d.
Fig. 39.
Fig. 39. A front view of the muscles of the trunk. On the left side the superficial layer is seen; on the right, the deep layer. 1, The pectoralis major muscle. 2, The deltoid muscle. 6, The pectoralis minor muscle. 9, The coracoid process of the scapula. 11, The external intercostal muscle. 12, The external oblique muscle 13, Its aponeurosis. 16, The rectus muscle of the right side. 18, The internal oblique muscle.
Practical Explanation. The muscle 1 draws the arm by the side, and across the chest, and likewise draws the scapula forward. The muscle 2 elevates the arm. The muscle 6 elevates the ribs when the scapula is fixed, or draws the scapula forward and downward when the ribs are fixed. The muscles 12, 16, 18, bend the body forward or elevate the hips when the muscles of both sides act. They likewise depress the rib in expiration. When the muscles on only one side act, the body is twisted to the same side.
Explain fig. 39. Give the function of some of the most prominent muscles, from this figure.