132 Disturbances of Circulation. 



In the presence of lime salts of the milk, casein (which is similarly a 

 calcium proteid combination) is separated from the milk bj' the lab- 

 ferment, leaving a serum, the \vhe\-. 



Coagulation of blood may be checked or inhibited by certain 

 chemicals which destroy the fermeiit or which dissolve the fibrin 

 immediately after it is formed (potassium citrate, or oxalate, extract 

 of the cephalic glands of the leech). [Extract of the cephalic end 

 of the hookworms of the dog possesses a similar property.] 

 So, too, coagulation fails if the inner surfaces of the vessel in which 

 the blood is caught be covered with vaseline, thus preventing adhe- 

 sion (Freund). 



After death the blood clots qtiickly and in a manner similar to 

 extravascular coagtilation, especially in the heart and larger vessels ; 

 in the capillaries it remains fluid for a longer time. In the presence 

 of toxic substances having solvent action upon the blocxl and fibrin, 

 too, coagulation is incomplete (hccmolytic sttbstances, as some of 

 the bacterial products, presence of excessive amounts of carbon 

 dioxide in the blood). Cadarcric clots are homogeneotis. soft, 

 elastic, gelatinous masses which look like casts of the vessels, are 

 without lamination, and are either of a dark red color throughout 

 or of a more or less yellowish gray to amber hue with jelly-like 

 semi-transparent appearance. The latter form, comparable to the 

 "buffy coat" are met in anaemic states and gradual cardiac failure, 

 the blood cells in such instances settling and the fibrin containing a 

 large amount of serum. [In these heart-clots the dark red homo- 

 geneous examples are commonly interpreted as indicating rapid 

 death and quick coagulation before the corpuscles have had time 

 to separate ; they are thus referred to as post-mortcui clots. On 

 the other hand, the yellowish translucent coagula. occurring in slow 

 circulatory failtire, are often spoken of as aiifc-iiiortciii clots, from 

 the idea that they form or start to form during the period of slow- 

 ing of the current prior to death, the red cells at least sinking 

 more or less from the general blood volume prior to the actual 

 stoppage of the current and coagulation of the blood.] 



Coagulation and thrombus formation within the vessels of the 

 living takes place from the following causes or favoring conditions : 



I. Entrance of chemicals into the circulation favoring coagula- 

 tion of the blood (fcnunit thrombosis) : B\- the injection of ether 

 and other chemicals, the introduction of substances destructive to 

 the leucocytes, injections of emulsions of various parenchymatotis 

 tissues (brain, adrenals) or of the expressed juices of the thymus 



