142 Journal of Comparative Neurology. 



millimeters for their respective lengths. This series was sup- 

 plemented by a yet unhatched but well-developed specimen 

 kindly furnished by the anatomical department. The entire 

 heads of these were sectioned serially in three planes, sagittal, 

 frontal and transverse, and were extremely valuable for compar- 

 ison with the adult. In addition to Neciiirus, the brain of 

 Dietnyctylus viridescens, Aniblystonia punctatam, and Desniogna- 

 thtis fiisca were examined, especially for the oblongata and the 

 origin of the cranial nerves, in order to confirm and better 

 interpret the results obtained in Necturus. For the relations 

 of the brain and nerves to the skull, and of the nerves to each 

 other, serial sections were made through the entire cranium; 

 for the study of the form and structure of the brain itself, how- 

 ever, it was removed. 



For fixing, were employed mercuric chloride and a 

 mixture devised by Dr. Fish ('93 ) and termed picroacetp-sub- 

 limate (Formula: 50 per cent, alcohol, looo c. c, glacial acetic 

 acid 10 c. c, mercuric chloride 5 grams, picric acid I gram.) 

 The latter gave the best results. The stains employed with 

 brains fixed as above, were hematoxylin with Van Gieson's 

 picro-fuchsin as a contrast stain which gave excellent effects. 

 The hematoxylins employed were Gage's ('92 ), Delafield's and 

 Herrick's modification of Delafield's formula ; all gave good re- 

 sults with possibly better figures when the last was used. Fish's 

 modification of Delafield's also was employed with good suc- 

 cess (addition of i c. c. of glacial acetic acid and i c. c. of a 

 saturated aqueous solution of corrosive sublimate to 100 c. c. 

 of the hematoxylin ). For the fiber tracts were employed 

 Weigert's hematoxylin method, and also one which is essen- 

 tially a modification of Exner's perosmic acid method (Ober- 

 steiner) the osmium being used in conjunction with platinum 

 chloride and acetic acid as in Hermann's solution. The 

 stronger formula of this was used and the brain fixed for 24 

 hours, washed well in water for 4-5 hours and imbedded in 

 collodion as usual, cleared and cut in Fish's castor-thyme oil 

 mixture. It was found that the method could be employed 

 also when decalcification was necessary, and that the blackness 



