Method of Treating und Mounting Celloidin Sections. 21 



and stretched out evenly upon the centre of a micro-slip ; the 

 superfluous oil was drained away and the remainder soaked up by 

 the use of filter paper. 1 then dropped a few drops of " Euparal 

 Mountant " upon the section and found that it was immediately 

 turned milky. I thought at first that this was due to my acci- 

 dentally breathing across the slide or possibly an excess of moisture 

 in the air. This is not an infrequent occurence when mounting 

 in " Euparal " under such conditions, particularly in the winter or 

 upon damp days. This is however easily and quickly dispersed 

 by slightly warming over the spirit flame, which I proceeded to do, 

 but to my surprise this milkiness could not be removed by this 

 means, and no amount of continued warming had the desired effect. 

 After trying a few methods to get rid of the milkiness without 

 success, I came to the conclusion that the action of the " Oil of 

 Thyme" upon the celloidin possibly produced a change which 

 made " Euparal " an unsuitable mountant, and therefore nothing 

 could be done but to use " Canada Balsam " in its place. 



As the refractive index of Canada balsam in this case was 

 higher than I wished for the sections under treatment, I left the 

 matter for a while in order to think over other possible causes 

 which might have produced the milkiness. After some amount 

 of meditation the thought occurred to me that knowing it was 

 possible to mount direct from 95 p.c. spirit into "Euparal" I 

 wondered if the latter would act as a clearing agent for celloidin. 



To my agreeable sur]:)rise and satisfaction I found that this ivas 

 the case. It remained only then to take the sections out of the 

 spirit on a lifter, transfer to the centre of the slide, spread them out 

 evenly, add a few drops of " Euparal," and cover with cover-glass, 

 and the preparation w^as so far finished. 



Occasionallv however, according to the amount of moisture 

 present in the atmosphere, or if one should accidentally breath 

 across the slide, a varying amount of milkiness may spread on the 

 surface of the " Euparal " 1 )efoie the cover-glass is applied ; but in 

 this case, as previously mentioned, it is at once dispersed by a 

 sliglit amount of warmth carefully regulated over the spirit flame. 

 It will be seen that as a result of this favourable action of 

 "Euparal" applied direct to celloidin sections taken from spirit, 

 that the use of a special cleaning agent prior to mounting is not 

 required; a most valuable saving of time and manipulation is thus 

 brou,^it about. 



There appears to be a very slight solvent action upon the 

 celloidin by the " Euparal," luit this need not in the least be 

 feared ; on the contrary it has a most desirable effect, so far that, 

 owing to this very slight action, any "frilling" or "puckering" 

 of the sections which may be apparent when they are spread out 

 upon the slide almost immediately disappears, and the section is 

 consequently flatted down and " partially cemented " as soon as the 



