340 JoiTRNAL OF Comparative Neurology. 



in turpentine and mounted in balsam dissolved in benzole. 

 The stain employed consists of Grenacher's hasmatoxylin 

 with the addition of a small proportion of corrosive subli- 

 mate and ammonium chloride. Seven and seven-tenths 

 grains sublimate and seven and three-tenths grains ammo- 

 nium chloride {i.e., one of Wyeth's compressed antiseptic 

 tablets supplies a quart of the fluid.(') 



The addition of the mercuric chloride not only acts as a 

 preservative, but improves the stain, especially in its effect 

 on the fibres. It remains unaltered for any length of time in 

 any climate, but before use it should be exposed to the air 

 in an open vessel for a number of days. Even when evapo- 

 rated to dryness it may be redissolved and filtered without 

 impairing its value. The resulting stain is a clear, trans- 

 parent, purplish blue when the fluid has properly aged. The 

 neuroglia scarcely stains, but the fibres are well brought out, 

 and cells (unshrunken and not enclosed in vacuoles) pre- 

 sent their characteristic structures most distinctly. The 

 presence of acid changes the color to a purplish red, between 

 which and the bluish tint are all gradations, depending on 

 the exposure to air. When thus prepared, the fish brain 

 yields to none in beauty and distinctness, and, because of the 

 very large size of the fibres and their sheaths, forms the best 

 subject for the study of tracts known to me. 



Rhinencephalon. 



In a previous paper the external topography has been 

 sufficiently discussed. (■') In the drum, where the olfactory 

 lobe is closely soldered to the base of the cerebrum, the 

 former is very obviously divided into a pes and pero portion, 

 as was, in fact, recognized by Sanders, whose description of 

 the ichthic olfactory lobe is most detailed of any with which 

 I am acquainted. I have elsewhere indicated the belief that 



1 Grenacher's hematoxylin is made by mixing 4 cc. saturated alcoholic solution of 

 hsematoxylin with 150 cc. strong ammonia alum solution in water, which, after a week or 

 two, is filtered and mixed with 25 cc. glycerine and 25 cc methyl alcohol. 



2 This journal, Vol. 1, p. 217-218, p. 228-233. 



