76 HISTOLOGY OP NUTRIENT FLUIDS. 



are embryonic or constructive, and others carriers of effete 

 matters, it is but natural that they should exhibit different 

 forms and act differently with reagents. The normal process 

 of disintegration of the red corpuscles may be exaggerated by 

 various morbid influences. They rapidly crumble into frag- 

 ments under high temperature, or from the action of chlorate 

 of potass, pyrogallic acid, sulphuric acid, certain poisonous 

 mushrooms, and the venom of some serpents. 



j. Variation in substances held in solution. 



I. Thrombi and emboli. When coagulation occurs in the 

 vessels during life the process is called thrombosis, and the 

 coagulum a thrombus. A fragment of a thrombus carried by 

 the blood until it is arrested in a smaller vessel is an cmbolus- 

 The formation of a thrombus may be seen in the web of a 

 frog's foot under the microscope by injuring the vessel me- 

 chanically or chemically. Thrombi formed during life are 

 distinguished from post-mortem clots by their greater firmness 

 and consistency. 



According to Schmidt's views, now generally adopted, 

 fibrin does not exist in solution in the blood, but results from 

 the interaction of two substances, yZ^rw/^gw/, which is held in 

 solution in the plasma, and fibrinoplastin , or paraglobulin 

 which, together with a third material or ferment, is held in 

 the white corpuscle. On the death of white corpuscles the 

 fibrinoplastin and ferment are set free, and, by their action 

 upon fibrinogen, produce fibrin. 



Coagulation within the blood vessels during life is prevented 

 by the motion of the blood, but chiefly by the integrity of the 

 endothelial lining. If the latter be destroyed, or the motion 

 retarded or stopped, the blood coagulates. When an artery 

 is tied coagulation occurs up to the first branch, and the 

 thrombus thus formed is red, since it contains all the elements 

 of blood, but when the lining endothelium is injured, the 

 white corpuscles adhere to the eroded spot, and by their death 

 produce fibrin, called the pale or parietal thrombus. This 

 may occur in the heart, an artery, vein, or capillary, or in the 

 lymphatic vessels. A portion of such thrombus may be 



