Electro-physiology and electro-therapeutics : showing the best methods for the medical uses of electricity / By Alfred C. Garratt.

The serratus magnus is mainly an inspiratory muscle, be- cause it acts in concert with other muscles, to elevate the ribs ; from which, indeed, it arises. It also contributes to lift the humerus. But the serratus posticus inferior is attached to the spinous process of the two lower dorsal, and the two upper lumbar vertebras, and is then inserted into the angles of the four lower ribs. The action of all these muscle fibres is for depressing the ribs, and concurs in expiration, and at the same time slightly aiding a slight rotation of the ribs upon the vertebras. The serratus posticus superior arises from the upper dorsal and one lower cervical vertebras, and is then inserted into the margin of the second, third, fourth, and fifth ribs. Its action is directly antagonistic to the serratus inferior, for it tends to raise the ribs upon the spine, and so elevate the chest as to concur in inspiration. If it is permanently contracted, it would produce dorso-lumbar curvature of the spine towards that side; if para- lyzed, the curvature would be towards the other side. The ser- ratus magnus, being a broad, flat muscle, arising from the first eight or nine ribs by digitations, and inserted into the spinal border of the scapula, when normal, sustains the scapula for- ward, and contributes to keep up its external angle against the weight of the upper arm, which is so continually tending to depress the external angle of the scapula. We see, then, that the trapezius and the serratus are both opposed to this depres- sion. But if the trapezius is paralyzed, or atrophied, or but fatigued and relaxed, then the external angle of the scapula is allowed to fall, more or less, while its inferior angle rotates upward and backward, so as to approach or override the spinous processes. And if the serratus magnus be also involved, as in a wasting palsy, then the external angle becomes even more depressed, while the inferior angle rises quite to the level of the external angle, and projects or hangs off hideously from the ribs. The splenitis colli and splenius capitis are two muscles that have a common origin at the six upper dorsal and last cervical spinous processes; then, again dividing, the latter goes to be in- serted in the mastoid process of the temporal bone. They act