144: 



THE BLOOD. 



The relative proportions of the serum and clot are very 

 variable, unless we include in our estimate of the serum that 

 portion which is retained between the meshes of the clot. 1 

 As the clot is composed of corpuscles and fibrin, and as these 

 in their moist state represent in general terms about one-half 

 of the blood (see table, page 138), it may be stated that after 

 coagulation, the actual proportions of the clot and serum 

 are about equal. If we take simply the serum which 

 separates spontaneously, we have a large quantity when 

 the clot is densely contracted, and a very small quantity when 

 it is loose and soft. 2 



Characters of the Clot. On removing the clot, after the 

 separation of the serum is complete, it presents a gelatinous 

 consistence, and is more or less firm, according to the degree 

 of contraction which has taken place. As a general rule, 

 when coagulation has been rapid, the clot is soft and but 

 slightly contracted. When, on the other hand, coagulation 

 has been slow, it contracts for a long time, and is much 

 denser. When coagulation is slow, the clot frequently pre- 

 sents what is known as the cupped appearance, having a con- 

 cave surface, a phenomenon which merely depends on the 

 extent of its contraction. It also presents a marked differ- 



1 It is estimated by Milne-Edwards that the clot retains, in most instances, 

 one-fifth of the entire volume of serum. Lemons sur la Physiologic, etc., tome L, 

 p. 124. 



a According to Thackrah the following are the periods required for the coagu- 

 lation of the blood in some of th inferior animals : 



Horse, Blood coagulates in from 5 to 13 minutes. 



Ox, 



Dog, 



Sheep, 



Hog, 



Rabbit, 



Lamb, 



Duck, 



Fowl, 



Pigeon, 



12 

 3 



H 



almost instantaneously. 



