SERUM OF THE BLOOD. ] 77 



mation; because if the coagulation be very rapid, it will pre- 

 vent the constituents of the crassamentum from separating from 

 one another, by entangling the red globules, in the coagulating 

 lymph. 



After death the blood is coagulated in the veins, .though not 

 so perfectly or generally as is supposed, for there are no sub- 

 jects which do not bleed from their large veins, when the latter 

 are opened. 



There are many modes of death which prevent entirely the 

 coagulation of the blood in the vessels, for example, where life 

 is destroyed by a paroxysm of excessive anger; by electricity; 

 by lightning; by a blow upon the stomach; by certain fevers 

 of a typhoid character. Many chemical, articles prevent its 

 coagulation on being mixed with it. 



SECT. I. OF THE SERUM OF THE BLOOD. 



Serum is common to the blood of all animals, and is consi- 

 dered, by Mr. Hunter, to be more abundant in such as have red 

 globules. It is, generally, of a lighter specific gravity than the 

 crassamentum. I have, however, often seen the latter floating 

 in it, which shows the contrary in some instances. Though its 

 separation commonly depends upon the coagulation of the lat- 

 ter, yet that process is not indispensably necessary, as was once 

 witnessed, by Mr. Hunter, in a lady, in whom the serum was 

 disengaged from the crassamentum, while the latter was yet 

 in a fluid state. The phenomena of dropsy, also, prove the 

 same point. 



Serum, though very fluid, is not so much so as water. It is of 

 a light yellow or straw colour, varying, somewhat, in different 

 subjects. It contains a large quantity of albumen, or matter re- 

 sembling the white of an egg. It also consists of water, of soda 

 uncombined, and of some of the salts of soda, the presence of 

 all which may be manifested in several ways. For example* 

 when exposed to a heat of 140 degrees of Fahrenheit, it becomes 

 opaque, and at 160 or 165 coagulates firmly. During this pro- 

 cess, a great deal of air is disengaged from it. It is also coagu- 

 lated by spirits of wine, by all the mineral acids, by corrosive 

 sublimate, and by many other articles, all of which prove the 



