114 AVE8. 



thoracic portion continues of nearly the same size as the upper part of the 

 cervical ; towards the loins it increases again, and becomes most enlarged 

 about the middle of the portion giving off the nerves to the lower extremities. 

 A little above and below this part there is a separation of the two posterior 

 halves of the cord at the ventricle, which is covered only by membrane ; 

 the spinal cord begins to diminish again, and becomes gradually less as it 

 approaches the extremity of the tail. In the dorsal and lumbar portions, 

 where no motion is allowed, the cord fills the spinal canal, and in many 

 parts is covered closely by a thin plate of vitreous bone. The anterior and 

 posterior bundles of each nerve are of nearly the same size ; and in one 

 of the largest nerves, the anterior bundle could not be so clearly separated 

 from the ganglion as in man, neither in the turtle. The cervical nerves are 

 very numerous, each of them is divided into an anterior and posterior 

 trunk ; the anterior is given to the muscles and the skin, and the posterior 

 principally to the muscles. The dorsal, after giving filaments to the 

 intercostal muscles and the rudiment of the diaphragm, pass to the skin 

 of the side ; the lumbar and some of the sacral form the nerves of the lower 

 extremity ; and the rest, to the termination of the spinal cord, are given 

 to the muscles and skin of the cloaca and tail. In the pinion very distinct 

 little muscles are observed for giving motion to the quills, and thus form a 

 variety of the cutaneous muscle. 



5. First of the three cervical nerves, which, together with the first dorsal, form 



the axillary plexus. The two preceding cervical nerves communicate 

 together, and then with the first entering the plexus, and are distributed 

 on the muscles at the posterior part of the scapula corresponding with the 

 trapezius, the levator of the scapula and rhomboid, and on the skin. Several 

 branches from the plexus are given to the pectoral muscles and that resem- 

 bling the great serrated. 



6. Circumflex nerve ; it gives a branch to a muscle analogous to the broadest 



muscle of the back, and is then distributed on the deltoid. 



7. Internal cutaneous nerve, descending, at the inner side of the humerus, to the 



skin. 



