1893.] THE MICROSCOPE. 45 



ijg. — What is the best method for resurrecting blood cor- 

 puscles from blood stains and clots* and how best mounted} — 

 H. M. F. 



No method has yet been devised which will satisfactorily re- 

 store dried blood. A prolonged soaking in a fluid of the same 

 specific gravity as blood serum, say a f% solution of salt, or a 

 glycerin solution, or some such fluid, will soften the clot, but the 

 corpuscles will never regain their normal form and size ; they 

 will be distorted, wrinkled, and shrunken. If one will consider 

 the extremely delicate and peculiar character of blood corpuscles, 

 it will be evident that changed blood cannot be completely re- 

 stored. If corpuscles be removed from the flowing blood current 

 by escaping into the tissues, or even when stagnated in the end 

 of a tied artery, a clot is formed and the corpuscles adhere to each 

 other. This is a physiological condition, the first stage of a dis- 

 organization and reorganization into a proper tissue, or at least 

 into a harmless tissue in the case of the tied vessel, when the 

 blood forms a fibrous plug, and later a harmless, shrunken cord. 

 If blood is designed to change rapidly for the purposes of nutri- 

 tion or repair, the restoration of a dried clot seems hopeless, but 

 the field is open for original work in this line. 



140. — Uozv may sections of vegetable tissues ifnbedded in cel- 

 lo id in, be stained and cleared so the cello idin will become 

 transparent ? — B. 



Tissues should be stained in bulk before being imbedded in cel- 

 loidin. This substance, being practically cellulose, will be 

 stained or discolored by nearly all the ordinary staining fluids, 

 and the color cannot be discharged except by a chemical, which 

 would also bleach the section. 



141 . — What is the duty on English ?nicroscopes imported 

 into the United States? — Dr. Evans. 



If for private use, 40 per cent, ad valorem. If for colleges or 

 schools, and so proven, free of duty. See article on this subject 

 in the Microscopical Journal for January, 1893. 



142. — / am troubled by the slozv hardening of my balsam 

 mounts. Can I use mild heat, or can you suggest so?ne other 

 ?nedium for quick work? — Amateur. 



All balsam solutions harden slowly after the exposed surface 

 has solidified. Mild heat is often used to hasten the hardening 

 of balsam mounts. If the object will bear it. the excess of solvent 

 may be boiled away, or evaporated more gently over a lamp be- 

 fore covering, and the cover applied while the balsam is hot. 

 When cold such mounts may be cleaned and finished imme- 

 diately. 



