CIRCUMSTANCES INFLUENCING COAGULATION. 245 



2. When the blood is surrounded by healthy living tissues, 



interchanges may occur between them, and if the oxygen 

 supply is deficient, coagulation is much delayed. Thus 

 considerable quantities of blood effused into the tissues 

 may be liquid and black for many days after its escape 

 from the vessels. This dark blood clots on removal and 

 exposure to the air. 



3. Low temperature. The rate of coagulation decreases with 



a temperature below 38 C., and the process is checked 

 at C. 



4. A great quantity of water seems to render the action of the 



fibrin factors weak. 



5. The addition of egg albumin, syrup or glycerin, retards the 



process. 



6. The addition of concentrated solutions of neutral salts 



(about three volumes of 30 per cent, solution of magne- 

 sium sulphate) quite prevents coagulation. 



7. The addition of small quantities of alkalies. 



8. The addition of acetic acid until very slight acid reaction 



is obtained. 



9. Increase in the amount of carbon dioxide. This, together 



with the want of oxygen, explains why venous blood 

 clots more slowly and loosely than arterial, and why the 

 blood in the distended right side of the heart is commonly 

 liquid after death from suffocation. 



10. The blood of persons suffering from inflammatory dis- 



ease coagulates slowly, but forms a very firm clot. 



Since the blood coagulates spontaneously when removed from 

 the body, the question now arises, how does it remain fluid in the 

 bloodvessels? 



Though this question has long occupied much attention, it is 

 still difficult to formulate a definite answer. Nor can we expect 

 to find any adequate explanation until we are better acquainted 

 with the exact details of the origin of the fibrin generators. It 

 must be remembered that the blood should be regarded as a tissue, 

 made up of living constituents requiring constant assimilation and 

 elimination for the maintenance of its perfectly normal conditions 



