The Microscope. 83 



We have made a magaificent beginniag and shall surely arrive at the 

 fullest measure of completion. As has often been said, Nebraska 

 has the ci-edit of being the first State in the Union to establish an 

 institution of this kind, and the results have certainly been such that 

 every patriotic citizen of the State can point to them with prida 



AN ALCOHOLIC ALUM-CARMINE STAIN. 



W. C. BORDEN, M. D., V. S. A. 



^"T^HE efficacy of the alum-carmine fluids in tissue-staining is 

 -^ well known. With them the nuclei of cells are shown pur- 

 ple, sharply defined, with clear details, and other elements are 

 slightly, but clearly stained of a lighter color. They are made by 

 boiling either carmine or cochineal in an aqueous solution of alum, 

 and are preserved by the addition of carbolic acid or chloral hydrat e. 

 Of the two methods, the one in which cochineal is used, in my 

 experience, gives the better results, but both are open to some 

 objections. First, as the stain is in aqueous solution, it is apt to 

 precipitate in the tissues, when alcohol is used either before or after 

 the application of the stain, unless the alcohol be entirely removed 

 before the stain is applied, or unless, after staining, the superfluous 

 stain be washed out, by rather pi'olonged soaking of the tissue in 

 water, before the application of alcohol. This is especially true if 

 the staining be done in bulk, and the larger the piece to be stained, 

 the longer it will take to remove the surplus stain. Second, the 

 stain is an excellent one for staining in mass, and as the tissue to be 

 stained must remain for some time in the fluid to allow thorough 

 penetration of the stain, often for a week or more if the piece is 

 large, or if the hardening has been done in a bichromate of potash or 

 acid fluid, this long immersion in an aqueous fluid is not desirable. 

 Third, for tissues hardened in potassium bichromate, or acid fluids, 

 the action of the stain is rather slow, even when the staining is 

 done after sectioning. 



For these reasons I determined to attempt an alum-carmine 

 stain, in which alcohol should enter largely; and, after various 

 attempts, settled upon the following as giving the best results: 



Cochineal (whole insects) 1 dram. 



Saturated solution of alum 4 ounces. 



95 per cent, alcohol 4 ounces. 



Pulverize the cochineal by grinding in a mortar, add the 

 saturated solution of alum and boil fifteen minutes, adding distilled 



