200 BLOOD. 



lettings. As, however, exceptions to these observations sometimes 

 present themselves, we must presume that other influences 

 frequently supervene which counteract the effect of the water. It 

 follows, therefore, that we are unable to draw any conclusions 

 regarding the relations of weight between the serum and the actual 

 coagulum, from the relative volumes of the clot and of the serum ; 

 since we should have .to consider in such an estimate, whether 

 the fibrin in its condensation had completely pressed out the 

 serum. 



Henle further draws attention to a mechanical influence, which 

 may give rise to the formation of a soft and very diffluent coagulum, at 

 least in some few cases ; for when the blood slowly flows in separate 

 drops, each drop forms, in a certain degree, a coagulum which does 

 not combine with the other drops to form a homogeneous and 

 connected mass. Henle assigns this as the cause of the incoagu- 

 lable character of the menstrual blood ; but Schmidt's and my own 

 observations (to which we shall refer in a future page) have 

 shown that this blood does not contain any fibrin. 



The gases contained in the blood appear to exert some influ- 

 ence on the consistence of the clot ; for whilst a light red, highly 

 oxygenous blood yields a dense, elastic coagulum, the clot appears 

 to be soft in all conditions in which the blood is rich in carbonic 

 acid ; this is especially manifested in asphyxia a condition in 

 which it has been asserted that the blood exhibits no capacity for 

 coagulation. 



It is not impossible that other constituents of the blood may 

 influence the consistence of the clot ; at all events we find in 

 artificial experiments with salts which retard coagulation, that a 

 soft and frequently even a mere gelatinous coagulum is formed. 

 The soft, friable, and often tar-like consistence of the clot in 

 putrid diseases, may therefore be owing to free alkalies or their 

 carbonates. 



We are unable, at the present time, to determine whether the 

 differences manifested in the physical character of the clot, depend 

 upon differences in the chemical constitution of the fibrin. Some 

 observers have conjectured that there are different kinds of fibrin ; 

 we have already spoken of parafibrin, &c., but no differences in 

 the nature of fibrin admit of being chemically demonstrated ; nor 

 are we logically compelled to assume the existence of such differ- 

 ences, since the different forms under which the fibrin coagulates, 

 may possibly depend upon the action of certain chemical relations, 

 of which we are still ignorant. When we remember that ordinary 



