THE PREPARATION OF ANIMAL TISSUES. 45 



When many different tissues are in fche same jar, 

 the quantity of fluid must be such that the upper 

 surface of the tissues extends half way up the entire 

 fluid, that is to say, the stratum of tissues and 

 stratum of clean fluid over them should be of equal 

 depth. 



Bichromate of Potass. 



Make a 2 per cent, solution of bichromate of 

 potass, with ordinary water. 



Meso-rectum of Cat. Pin this out on cork, and 

 float it cork upwards on the solution for seven 

 days. 



Liver. After injecting the portal vein with blue 

 gelatine mass, and the hepatic artery with carmine 

 gelatine mass, the liver may be hardened in the 

 solution to toughness, and, of course, finished in 

 alcohol. 



Spinal Cord of Ox. Pieces an inch long may be 

 placed in the solution frequently changed for 

 from three to five weeks. 



Spinal Cord of Ox, Horse, or Sheep. If pieces 

 about an eighth of an inch long be macerated two 

 or three days in -J per cent, of the solution, 

 the anterior horn of the spinal cord snipped out 

 with scissors, and teased in carmine solution, then 

 pressed with a cover glass, using Farrant's medium, 

 they will show the isolated multipolar nerve cells 

 very beautifully. The sympathetic nerve cells of 

 the frog can be isolated in the same manner. 



Cornea of cat, rabbit, or guinea-pig should also 

 be hardened in a 2 per cent, solution for ten 

 days. The lens in 1 per cent, solution for one 

 week. 



