296 SUMMARY OF CURRENT RESEARCHES RELATING TO 



character, &c., the process is finished by transferring the specimens 

 to 25 per cent., 50 per cent., 75 per cent., and absolute alcohol 

 successively. 



Where a tissue has become too deeply stained with osmic acid, it 

 may be bleached by putting it into a weak aqueous solution of ferro- 

 cyanide of potassium, care being taken afterwards to thoroughly wash 

 the section in water. The cyanide of potassium will effect the same 

 purpose, but must be used with care. 



Infusoria, algae, and other objects, killed, fixed, and stained with 

 osmic acid, have been mounted nearly a year, and show no signs of 

 change as yet. It is also especially valuable in examining the white 

 blood-corpuscles (as it instantly kills and fixes the pseudopodia), and 

 in bringing out clearly glandular, nerve, and fatty structures, and 

 tissues. Sudorific, sebaceous, and other glands are better brought 

 out by its use than in any other method that the author has used. 

 A specimen of the meibomian glands of the upper eyelid is excep- 

 tionally fine and beautiful. It is also very valuable in differentiating 

 all structures affected by fatty degeneration, particularly in the early 

 stage of this regressive action. 



Carbolic Acid in Mounting.* — Mr. W. J. Pow points out that 

 contrary to the general ojjinion, carbolic acid is not an acid, and has 

 no acid j^ioperties whatever. Chemically speaking it is an alcohol, 

 belonging to a series of alcohols quite different in composition from 

 common ethyl-alcohol, and from wood-spirit, which is closely related 

 to common alcohol. But carbolic acid is, nevertheless, a true alcohol, 

 and for this reason it can be frequently substituted for ethyl-alcohol 

 in microscopical work. One great advantage which it has over the 

 latter is found in the readiness with which it penetrates a specimen, 

 and mixes with the flui Is used in mounting, such as water, glycerine, 

 and Canada balsam. Another is, that it does not harden tissues and 

 make them stiff. For this reason insects, or parts of insects, can be 

 preserved indefinitely in carbolic acid, in a fit condition to be mounted 

 at any time. The more delicate parts are made quite transparent by 

 long soaking in the solution, but this is no detriment to them. 



The acid used for mounting should be the strongest solution, having 

 just enough water in it to keep it fluid at ordinary temperatures. To 

 use it for mounting, it is only necessary to drop the sj^ecimen into the 

 acid, and in a few moments transfer it to the prepared cell containing 

 the medium in which it is to be mounted. Suppose it is desired to 

 mount a mosquito, or a plant-louse, or any minute insect which requires 

 no preliminary treatment, drop the insect into the acid, and in a few 

 minutes it will be seen that the fluid has thoroughly penetrated the 

 body. Then it is quite immaterial whether the specimen is to be 

 mounted in Avater, or glycerine, or balsam, for carbolic acid will mix 

 as readily with one as with the other. Fill the cell with the medium 

 to be used, place the specimen on a clean slide, and take up the excess 

 of fluid with blotting-paper, then transfer it to the cell, and arrange 

 the parts with needles, when the cover-glass can be applied. 



* Amcr. Moil. Micr. Journ., iv. (1883) pp. 8-9. 



