66 THE MICROSCOPIST. 



vessels to be first injected, as with fine, transparent blue, 

 and the germinal matter to be stained with carmine. A 

 few drops of a solution of chromic acid, or bichromate of 

 potash, so as to impart to the glycerin a pale straw color, 

 serves to harden even the finest nerve-structures. Acetic 

 acid, and other reagents also, are much more satisfactorily 

 used with glycerin than with water. If syrup is used, 

 camphor, carbolic acid, etc , must be employed to prevent 

 the growth of fungi, but pure glycerin is free from this 

 inconvenience. 



A great advantage of this mode of investigation con- 

 sists in the fact that a specimen thus prepared is already 

 mounted, and needs but a proper cement to the glass cover 

 and a finish to the slide, when it is ready for the cabinet. 



FLUID MEDIA. 

 1. INDIFFERENT FLUIDS. 



The vitreous humor, amniotic liquor, serum, etc., which 

 form the usual fluids termed indifferent, always contain 

 what Prof. Graham designated colloid and crystalloid 

 substances. In 1 000 parts there are about 4 parts of col- 

 loid (albumen) and 7.5 of crystalloid substance (chloride 

 of sodium). 



The iodine serum of Schultze consists of the amniotic 

 fluid of the embryo of a ruminant, to which about 6 drops 

 of tincture of iodine to the ounce is added A small piece 

 of camphor will preserve this from decomposition a long 

 time. A substitute for this is composed of 1 ounce of 

 white of egg, 9 ounces of water, 2 scruples chloride of 

 sodium, with the corresponding quantity of tincture of 

 iodine. 



