The alligator and its allies

by A. M. Reese

The Spinal Nerves

As was noted above, the dorsal roots of the first two spinal nerves are lacking.

I, II, and III. The ventral branches of these three nerves supply the smaller, ventral neck muscles.

IV. The ventral branch of this nerve innervates with its chief divisions the ventral muscles, the sphincter colli, and the integument of the neck, and sends a small branch to the levator scapulæ superficialis muscle.

V. The ventral branch of this nerve sends branches to the ventral muscles of the neck, to the levator scapulæ superficialis; a large branch goes to the sterno-mastoid; and the rest of the nerve distributes itself in the sphincter colli and the integument and ventral muscles of the neck.

VI. The sixth nerve distributes itself to the ventral musculature and to the integument of the neck, and sends a fairly strong branch to the levator scapulæ superficialis muscle and to the most anterior part of the collo-thoraci-suprascapularis profundus muscle.

VII. The seventh nerve is the first to enter, by a small branch, into the brachial plexus ([Figure 31]). It also sends a branch to the ventral muscles and the integument of the neck, and three branches to various shoulder muscles.

VIII. The ventral branch of the eighth nerve ([Figure 31]) is the second largest nerve of the brachial plexus. It gives some twigs to the ventral muscles and then gives one or two nerves to the collo-thoraci-suprascapularis profundus and the serratus superficialis muscles. The rest of the nerve divides into an inferior and a superior branch which unite with the ninth nerve.

IX. The ninth and tenth nerves are the largest of the brachial plexus. The former, after giving off some twigs to the ventral musculature and to the serratus superficialis and the hinder regions of the collo-thoraci-suprascapularis profundus muscles, unites with the tenth nerve just after giving off the small thoracicus inferior nerve to the costo-coracoideus muscle. After uniting with the tenth nerve the ninth nerve immediately divides into two branches that form loops with branches of the eighth nerve, the whole making a very complicated plexus.

X. The tenth nerve, as noted above, is one of the two largest nerves of the brachial plexus. After giving off a single nerve to the ventral musculature, this nerve unites with the eleventh nerve; it then gives a branch to the costo-coracoideus muscle and forms a loop with the ninth nerve. After giving off a couple of nerves it again divides into two equal branches which unite with similar branches of the eighth nerve.