XXX Journal of Comparative Neurology. 



glass slips by means of Mayer's albumen, first flattening them out on 

 warm water if necessary to remove all wrinkles, and after passing out 

 of the absolute alcohol it is well to flow over each slide a very thin so- 

 lution of celloidin, draining quickly and allowing to set for a moment 

 before passing down into the lower grades of alcohol. The celloidin 

 film will prevent the loosening of the sections in the staining fluid, 

 which will sometimes occur with any other mode of fixing the sections 

 to the slide, and will in no way interfere with subsequent manipulations, 

 except slightly to retard them. If a thicker film is used the previous 

 use of the albumen may be dispensed with and the film bearing the 

 sections may be cut off from the slide and carried through the subse- 

 quent manipulations whole just like an ordinary celloidin section, though 

 for serial section work I much prefer to keep the sections fixed to the 

 slide on which they are to be permanently mounted. With the thin 

 celloidin film the final dehydration should be done in origanum or 

 carbol-xylol, though if the sections are thin I have not usually experi- 

 enced any difficulty in dehydrating in absolute alcohol, as the stay in 

 the strong alcohol can be so shortened as to remove the danger of the 

 solution of the film. The sections are mordanted and stained on the 

 slide in photographic trays or in staining tubes, the Coplin staining jar 

 (Queen and Co.) being the best jar for the purpose ; and in all of my 

 experiments these processes were carried on at the ordinary summer 

 temperature except where otherwise noted. Doubtless some of my re- 

 sults would have been diff"erent if the more usual celloidin embedding 

 and mordanting in the block had been followed, and especially if the 

 incubating stove had been employed during the process of mordanting; 

 yet from my experience thus far in the matter I am inclined to think 

 that these are factors of relatively slight importance and that more de- 

 pends on the relations of chemical affinity within the tissues than upon 

 accidents of temperature and other physical features of that sort, though 

 there is no doubt regarding the value of mordanting and staining at 

 blood heat to shorten the times of these processes. 



For the composition of the fluids mentioned, when this is not given, 

 the reader is referred to BoUes Lee's Vade Mecum, 



In most cases the processes of fixation and decalcification were 

 carried on together by means of the same fluid. First, the more usual 

 decalcifiers, nitric acid, picric acid, etc., were tried in various combi- 

 nations and these were afterwards replaced by acids which give a more 

 faithful fixation. In the following summary the trials will be arranged 

 first under the head of the fixing fluids, and under each of these the 

 several mordants and stains. Only two kinds of fishes were employed 



