THE MICROSCOPE. 51 



ination, take a fair piece, not merely a thin slice from the surface or 

 bottom, but a portion about three-fourths of an inch in thickness, 

 extending from the peripheral part of the growth to the centre so 

 that the histological conditions of the various parts of the growth 

 may be studied and also its method and area of invasion. For very 

 hard subcutaneous growths, such as scirrhus tumors of the breast, 

 and chronic inflammatory ma.sses, where we wish to study the rela- 

 tions of the rete. Malpighii to the growth, I prefer a very dilute 

 solution of chromic acid, say one-sixth or one-tenth per cent, in 

 water, as this causes less shrinkage then the methylated spirit, and 

 renders the sections less brittle, and also does not interfere with 

 their staining, since a section which has shrunken under the action 

 of spirit will not take staining fluid nearly so well as one in which 

 the shrinkage is not so great. 



For pathological changes in the alimentary canal, I prefer a 

 mixture like the following, — one part chromic acid solution of one- 

 sixth per cent, two parts methylated spirit, and one part water. The 

 material should be left in this fluid for five or six days, the fluid be- 

 ing changed occasionally in the mean time. 



For p.Tithological changes in the liver, I prefer a solution of 

 chromic acid of one-sixth per cent, and the material may remain in 

 the solution for six or eight days. For pathological changes in the 

 kidney I use a 5 per cent, solution of mono-chromate of ammonium, 

 and leave my material in solution for eight or ten days. For shov/- 

 ing pathological changes in connection with the brain and spinal 

 cord the best hardening fluids are either a two per cent, solution of 

 potassium bichromate or ammonium bichromate. 



After taking any material from any hardening fluid it is generally 

 necessary to leave it for an hour or two in clean water, and when 

 chromic acid or chromates have been used it may be necessary to 

 leave it six or eight hours in water, until it is washed free from the 

 yellow color which is imparted to it from the acid. The pieces are 

 then placed in absolute alcohol for ten or fifteen minutes and are 

 then embedded. 



For embedding I use equal parts of white w;ix and olive oil. 

 * * * *." — Dr. C. Beard, in the Canada Lancet. 



Carbon and the CiF.r.m Theorv. — In an interesting article 

 on the above subject, in the American Mont/i/y Microscopical Jour- 



