68 STUDIES IN ADVANCED PHYSIOLOGY. 



Without going into the many controversies of this prob- 

 lem, the most generally accepted theory is here given in 

 explanation of coagulation ; but it must be remembered that 

 many points are not yet clear, and that the observations of 

 the future may materially change our present notion. Ac- 

 cording to the observations of Alexander Schmidt, later 

 modified by Hammarsten, there are in the blood three main 

 albumens. These are fibrinogen, fibrinoplastin, sometimes 

 called paraglobulin, and serum albumen. The serum 

 albumen takes no part in the coagulation, and its purpose 

 in the blood is to afford a nutritive substance for the tissues. 

 If the blood plasma had no other function, this one albumen 

 would no doubt suffice as a food for all cells of the body ; 

 but as serum albumen clots only when subjected to the 

 action of heat or strong chemical reagents the coagulation of 

 the blood would be impossible, and the danger from hem- 

 orrhages would be always imminent. To prevent this loss 

 of blood other albumens are added. Of these, fibrinogen 

 possesses the property of being easily changed into fibrin 

 under certain definite conditions. To follow these suc- 

 cessive stages in detail let us imagine the finger suddenly 

 cut. As soon as the incision is made into the flesh and the 

 vessels traversing it, the blood finds itself in an abnormal 

 condition and the blood tablets at once begin to disinte- 

 grate, no doubt because they are not able to live under the 

 changed environment. In their disintegration they form a 

 substance which is called fibrin ferment. This fibrin fer- 



Fig. 17. NETWORK OF FIBRIN THREADS RADIATING FROM SMALL CLUMPS OF BLOOD- 

 PLATELETS. (After Schafer.) 



ment at once reacts upon the fibrinogen, causing that to 

 change into fibrin, and thus a clot arises. A somewhat 

 analagous case might be cited in the curdling of milk by 



