66 STUDIES IN ADVANCED PHYSIOLOGY. 



observers as varying from eighteen thousand to twenty-five 

 thousand in a cubic millimeter of blood. They break down 

 with remarkable rapidity as soon as blood is shed, and this 



Fig. 16. BLOOD CORPUSCLES AND PLATELETS IN A SMALL VEIN OF THE RAT'S MESEN- 

 TERY. (After Osier.) 



probably may account for the fact that they were only re- 

 cently discovered. Just where these come from is still a 

 matter of question. By some they are believed to be merely 

 parts of disintegrated white corpuscles, but as they have 

 been observed in the circulating, unharmed blood, this view 

 is probably not correct. Possibly they are nothing more 

 than very small white blood corpuscles. A very important 

 role has been assigned to these little plates, because it is 

 believed by a number of physiologists of rank that in the 

 disintegration of these plates the fibrin ferment is formed, 

 which starts the coagulation of the blood. The fact that 

 they disintegrate so rapidly when the blood is put under an 

 abnormal condition may be for the purpose of setting going 

 at once this process of coagulation. 



Historical. The colorless corpuscles were discovered by Hewson, and 

 their amoeboid motions, in the case of human corpuscles, by Davaine in 1850. 

 The blood tablets were first described by Bizzozero. 



THE BLOOD PLASMA. 



The liquid part of the blood is called the blood plasma. 

 When the corpuscles are removed from it it has a clear, 

 slightly yellowish color, a rather insipid sweetish taste, is a 

 little alkaline in its reaction, and of a specific gravity a little 

 greater than water. Its most striking property is its power 

 to form in a rather short time a so-called clot, and a thor- 

 ough understanding of the composition of this liquid must 

 be preceded by a discussion of the process of coagulation. 



