Herrick, Morphology of Braifi of Bony Bishes. 335 



true of the methods of neurological technique. It may be 

 replied that a necessary condition of the sharp differentiation 

 of one set of structures is the failure to develop or the diverse 

 modification of other tissues adjacent; it may even be con- 

 tended that this divergent modification is the essence of 

 differential staining, etc. Notw^ithstanding this objection, 

 we contend that for general purposes that treatment is best 

 w^hich brings out cells and fibres, neuroglia and nutrient 

 tissues most nearly in their normal relations. This conclu- 

 sion does not weigh against the use of special fibre stains or 

 metallic impregnation where a specific investigation of the 

 fibres is intended, but it suggests that such studies should be 

 controlled by recourse to a method which shows fibres in 

 their normal relations to cells, etc. It is also obvious that 

 for the general purpose a stain which brings out all the 

 cells of a given type in a vmiform manner is better than a 

 brilliantly selective stain which is also elective of one cell 

 and not of its neighbor of the same sort. The same consid- 

 eration renders a stain applied in section more reliable than 

 one used in toto with the inevitable danger of afl'ecting super- 

 ficial structures more than deeper ones. 



In the present case we fortunately have in a modification 

 of methods long since familiar all that is needed for a reason- 

 ably good cotemporaneous differentiation of the important 

 elements of the brain. 



METHODS. 



The removal of the brain is attended with considerable 

 difficulty in many cases. It will be remembered that the 

 brain of fishes is usually included in a cavity much larger 

 than itself, and is enveloped in a large and more or less 

 closely adherent sheath of loose adipose tissue, which sepa- 

 rates it from the cranial walls except ventrad. It freqently 

 is most difficult to remove the fatty mass without distorting 

 or injuring the pallium, the dorsal sac, and the epiphysis. 

 The great plexus of blood-vessels which is connected with 



