98 APPLIED PHYSIOLOGY 



to clot very slowly, and prior to operations in such cases 

 surgeons often administer calcium chloride in full doses, 

 with, it is stated, very satisfactory results. The same 

 drug is also useful in preventing haemorrhage in scurvy. 

 Albumoses appear to have a power of inhibiting coagula- 

 tion. In a fluid secreted by the mouth of the leech this 

 is made use of to prevent clotting in the bites, for such 

 fluid is found to contain an albumose, and it is so efficient 

 in its action that serious haemorrhage may take place 

 from the bites of leeches applied medicinally. There 

 is an impression amongst some clinical observers that 

 the administration of ammonia salts also tends to lessen 

 the coagulability of the blood, and such salts have been 

 given in cases of threatened thrombosis. I am not 

 aware, however, of any direct experimental evidence in 

 support of such a belief. Gelatin, on the other hand, 

 promotes coagulation, and has been largely used by 

 subcutaneous injection to increase the clotting power of 

 the blood in cases of aneurysm. 



Clotting may be regarded as the death of the blood, 

 for the serum which is squeezed out of the clot is, as 

 compared with the plasma, de- vitalized. If injected into 

 another animal, its constituents are broken down and 

 excreted, the output of urea being raised. Thus serum 

 can be regarded as a food. After the injection of plasma, 

 on the other hand, no rise in nitrogenous output can be 

 observed. 



Serum contains all the constituents of plasma except 

 fibrinogen, and in addition it holds in solution the pro- 

 ducts of disintegration of leucocytes ; and amongst the 

 bodies interesting to the pathologist which have been 



