ESTERLY: EUCALANUS. Z 
cutting paraffine sections. ‘The treatment ordinarily given material 
intended for microscopic investigation is sufficiently satisfactory in 
this case, but to prevent shrinkage and distortion, care is necessary 
in the use of the higher grades of alcohol, in clearing and in transferring 
to paraffine. 
In dehydrating, I have made it a practice to transfer the material 
from 90% alcohol to 95% alcohol and then after 5 or 10 minutes to 
replace this by absolute alcohol. Xylol has proved to be the best 
clearing agent. If this is added drop by drop to the absolute alcohol 
until the mixture has reached the proportions of 4 alcohol and 2 xylol, 
and then pure xylol is used, the animals will clear quickly and without 
the least shrinkage. Before transferring to the paraffine used for 
imbedding it is well to allow the object to remain for a time in a 
saturated solution of paraffine in xylol. I have always used for 
imbedding purposes a paraffine which melted at 60° C. and sections 
were generally cut 10 4 in thickness, though sections 6 » in thickness 
are readily obtained. It is not necessary to employ a reagent for 
softening or destroying the chitinous covering of the animal, for, after 
any fixation employed, perfect sections and ribbons can be obtained. 
The chief trouble has been to preserve the animal in its normal form, 
so that it might be oriented for cutting sections in particular planes. 
Dehydration and clearing take place very rapidly, but infiltration 
with paraffine is slower. It is well to leave the animals in melted 
paraffine for an hour or a little longer. 
I have relied chiefly upon a modification of one of vom Rath’s 
mixtures and upon Zenker’s fluid for killing and fixing reagents. 
Saturated aqueous corrosive sublimate and a corrosive-acetic mixture 
have likewise been employed, as has also 10% formalin; but Zenker’s 
fluid is by far the most satisfactory of all these reagents. The osmic 
acid mixture of vom Rath was modified slightly in the amount of 
platinic chloride. ‘To a mixture containing 12 c. c. of 2 % osmic acid, 
100 c. c. saturated aqueous solution of picric acid, and 1 ¢. ec. of acetic 
acid, I added 25 c. ce. of a 0.2% solution of platinic chloride. This 
has given satisfactory results. It has been allowed to act for varying 
lengths of time upon animals put into it from sea-water, and has in 
some cases been followed by pyroligneous acid, as recommended by 
vom Rath (’95). I believe it is better to allow the fixative to act alone 
and for not more than 36 hours, otherwise the blackening is so great 
as to detract from the value of the preparation. When the fluid is 
used for that time without further treatment the medullated nerve 
fibres are blackened intensely, while the rest of the nervous system 
