The Microscope. 245 



specimen. A stain which, for instance, prefers the connective tissues, 

 can be used and then followed by one partial to epithelium. The 

 contrast in a specimen containing these elements and thus stained 

 will be very marked. These stains can often be combined in one fluid, 

 when, with two, it is called -a double-stain; with three, a treble- 

 stain, etc. 



Though the number of stains is very large, only a few will be 

 given here — sufficient, however, for nearly all histological work. If 

 properly used they will be found to give excellent and sharp defini- 

 tion. They may be classified in this manner: 

 General Stains: 



Ammonia-carmine, 



Glycerine-carmine, 



Picric acid. 

 Selective Stains: 



Hsematoxylin, 



Silver nitrate, 



Osmic acid. 

 Dou.ble Stains: 



Picro- carmine. 

 The formula for ammonia-carmine will be found in the last les- 

 son. This is an old and tolerably good stain, but it does not give a 

 pure carmine tint. This is due, probably, to the small amount of 

 ammonia remaining. Again, the solution tends to turbidity and 

 decomposition, especially when the ammonia is finally lost. To pre- 

 vent this precipitation and decomposition, and to retain the ti-ue car- 

 mine color, Joseph W. England, Ph. G., gives a formula in the 

 American Journal of Pharmacy for July, 1887, which, though 

 designed for a different purpose, the writer has tried as a stain with 

 most satisfactory results. It works evenly and quickly, and imparts 

 a most delightful color. The following is the formula: 



GlYCEEINE- CARMINE. 



Carmine, (No. 40) 4 drachms. 



Water of Ammonia, 8 fluid- ounces. 



Glycerine, 3 fluid-ounces. 



Water, q. s to 8 fluid-ounces. 



" Rub the carmine into a fine powder, in a wedgwood mortar, 

 make a paste with and dissolve in the water of ammonia and then add, 

 with constant trituration, the glycerine. Transfer to a porcelain 

 capsule and heat upon a water-bath, until the liquid is entirely des- 



