ADDITIONS. 



Platelets of Blood. (Blutplattchen.) The platelets 



are colourless bodies about J the size of the red 

 corpuscles; in shape fairly like the red corpuscles, 

 and nucleated when the red corpuscles are nucleated. 

 They very readily break down into formless granular 

 masses. In the frog or newt they are readily seen 

 in the capillary circulation of the mesentery or 

 other part of the animal. During inflammation (cp. 

 p. 133) they will be seen clinging in numbers to the 

 inner walls of- the small vessels. They may also be 

 seen in a drop of blood if it is examined immediately 

 after being drawn from the body; certain fluids 

 retard the rate of disintegration of these corpuscles, 

 the corpuscles are longer preserved if a little blood 

 be allowed to run from the body into 3 to 5 times 

 its volume of one of the following : sodium chloride 

 6 p.c. with a little methyl-violet (about 3 c.c. sodium 

 chloride solution and one drop of a strong aqueous 

 solution of methyl-violet); 20 p.c. magnesium sul- 

 phate; 1 p.c. osmic acid. 



HARDENING AGENTS. 



Mercuric Chloride. A saturated aqueous solution is a 

 good general hardening agent for glands and epi- 

 thelium of skin and cornea. The tissue is left in 

 the mercuric chloride solution for several days, 



252 



