CONTRIBUTIONS TO THE COMPARATIVE MOR- 

 PHOLOGY OF THE CENTRAL NERVOUS SYS- 

 TEM. 



II. —Topography and Histology of the Brain of Certain Reptiles. 



(Continued from Vol. III. p. io6. With Plates XV-XX.) 



By C. L. Herrick. 



In seems desirable to supplement the previous instalment 

 by a few data derived from a comparison with Amphibia and 

 from an application of the Golgi method. The turtle and 

 Anura have much in common in the structure of the fore-brain, 

 while the Urodela displays a still greater simplicity of structure. 

 In general, it may be said that a comparison of the two types of 

 amphibian brain affords very strong evidence in favor of the 

 view that all nervous elements are modifications of a single 

 typical neuroblast. In Menopoma, for example, all of the brain 

 regions retain very much of the embryonic simplicity. The 

 structure of the optic lobes does not appreciably differ from that 

 of the cerebrum or olfactory tuber. The connections via the 

 various tracts, however, remain practically as in higher forms. 

 In the Anura the optic lobe acquires the stratified structure 

 found in turtles and fishes, and other regions are equally com- 

 plicated. Suitable methods show that the idea that the Am- 

 phibian brain is chiefiy composed of disconnected granules is 

 erroneous, for the size and ramification of the processes of the 

 cells is marvelous. 



Application of iJic Golgi method to the tiiftle brain. In con- 

 nection with the data by the haematoxylin method, which is 

 certainly most reliable, we have employed the method of silver 

 impregnation. It is possible to use it readily in connection 

 with the familiar process of paraffin imbedding. The fragments 

 are passed into 90 per cent, alcohol from the nitrate of silver and 

 then into absolute. They are then imbedded in parafifiin in the 

 ordinary way and mounted in benzole balsam, covering at once, 



