SPINAL CORD. 12 



the bichromate, make it veiy evident that some of these fibres are close- 

 1\- related to the prolongations of the nerve cells, and Plate XXXIII. 

 from a chromic acid preparation, demonstrates the fact, that many of the 

 axis-cylinders of the inferior roots, in the frog, can be followed well into 

 the gra}' substance and are lost among the large cells. 



Contraiy to the opinions of both Reissner and Stieda, I know of no 

 other animal in which so many of these axis-cylinders can thus be traced, 

 in sections of chromic acid preparations. 



Areas of Gray Matter in Cross Sections, from the 



Tivo Enlargements, Compared. 



Saurians Cenical equals Lumbar. 



Testudo Polyphemus. Ant. more developed 



than Post. Extremities. " exceeds " 



Testudo Viridis. Ant. much more developed 



than Post. Extremities. " much exceeds " 



Emys Floridana. \ _, 



Post, more developed 

 " Terrapm. ;- . . " equals 



^ . \ than Ant. extremities. 

 Cistud. Carolina. ) 



Chelydra S. Extremities about equal. Lumbar slightly exceeds Cervical. 



Rana. . . . Post, more developed 



than Ant. extremities. Cei^ical " " Lumbar. 



In all chelonians, the cervical is much longer than the lumbar en- 

 largement. As before stated, in the frog, the lumbar enlargement is 

 the longer; while in saurians, the}- are more nearly equal in length. 



The author does not intend, by the facts here tabulated, to be un- 

 derstood as advocating an-\- theory, and the same ma}- be said of the ta- 

 ble on page lo. 



