74 Journal of Comparative Neurology 



Material and Methods. 



In preparing the following paper the aim has been to study 

 the general morphology of the turtle's brain. While histological 

 methods have been necessary for the study of parts that were 

 too small and delicate for study by gross methods, no attempt 

 has been made to give the details of histological structure. The 

 material used consisted mainly of a number of brains of adult 

 snapping turtles (Chelydra serpentina), collected during the sum- 

 mer of 1893, in western Indiana. To the Anatomical Depart- 

 ment of Cornell University, I am indebted for some valuable 

 embryo brains, without which my work would have been much 

 less satisfactory. Acknowledgements are also due to Mr. A. 

 T. Kerr, Jr., a student of Cornell, for some valuable material. 

 In addition to this I had for comparative study specimens of 

 Chrysemys picta and several specimens of the large sea turtle — 

 Clielone midas — kindly furnished by the department. Prof. 

 Wilder also generously put the large collection of reptilian 

 brains in the University Museum at my command. These, con- 

 taining as they do, many dissected preparations, were invalua- 

 ble as a source of comparison for gross anatomy. I can only 

 regret that lack of time rendered my work in this regard very 

 incomplete and unsatisfactory. 



Methods. — Various methods of hardening were employed. 

 For adult brains potassium bichromate, zinc chloride, picric al- 

 cohol, Fish's alcohol-zinc chloride-glycerine method and alcohol 

 were used. By the methods used for staining I found but little 

 difference as to results except for the bichromate. Brains hard- 

 ened in this did not show the cellular parts so well but were best 

 for tracing the fibre tracts. For small turtles the skull was de- 

 calcified and sectioned. Embryos were placed in Perenyi's 

 liquid for decalcification and hardening, and were then sectioned 

 through the entire head. Sections of all forms were made in 

 the three principal planes, — frontal, sagittal and transverse. All 

 the preparations were imbedded in collodion and sectioned in 

 Fish's castor-thyme oil mixture. This method has many excel- 

 lencies to recommend it for nervous tissue. The stains used 



