MOUNTING OBJECTS. 31 



dishes are kept scrupulously clean, and the same care must be be- 

 stowed upon the needles, forceps, etc. 



You may, of course, stain several sections at once, providing you 

 take care to keep them from rolling up or sticking together. 



While the vessels which I have recommended will be found of con- 

 venient, proportionate, and economical size for general work, larger 

 ones are sometimes needed; and almost any glass or porcelain vessel 

 may be impressed for duty. 



CARMINE AND PICRIC ACID STAINING. 



After having washed the tissue, subsequently to mordanting with 

 oxalic acid in the borax- carmine process, a bright yellow may be 

 communicated to certain anatomical elements by means of picric acid. 

 This often gives a valuable differentiation. 



The sections are placed in the picric-acid solution and allowed to 

 remain for ten minutes. Kemove to water one ounce, glacial acetic acid 

 ten drops for a moment, to fix the yellow; after this dehydrate with 

 alcohol, and clarify with oil of cloves as usual. The sections should 

 be transferred to the picric and acetic acid solutions by means of a 

 platinum wire or a minute glass rod. The ordinary needle would be 

 corroded, and the sections thereby discolored. 



MOUNTING OBJECTS. 



CLEANING SLIDES AND COVERS. 



When purchasing "slides, let me urge you to get them of good 

 quality. The regular size is one by three inches, and the edges 

 should be smoothed. As furnished by the dealers they are usually 

 quite clean, and only require rubbing with a piece of old linen to 

 prepare them for use. 



The cover-glasses should be thin, not over T J^th of an inch, called 

 in the trade-lists " No 1." Circles or squares three-quarters of an 

 inch in diameter are generally convenient. They must be thoroughly 

 cleaned: Drop them singly into a saucer containing hydrochloric 

 acid. Then pour off the acid, and let clean water run into the dish 

 for several minutes. Drain off the water and pour an ounce of alco- 

 hol on the covers. Kemove them one at a time with the forceps or 

 needle, and wipe dry with old linen.* The glass may be held between 



* We are indebted to Professor Gage, of Cornell University, for suggesting 

 the use of Japanese tissue paper for wiping cover glasses, lenses, etc. Or- 

 dinary manilla toilet paper is also an excellent material for such work. 



