COAGULATION 45 



and believed to be the simplest proteins) exert, when injected 

 intravenously, a retarding influence on coagulation, and lower the 

 blood-pressure,, just as albumoses do (Thompson). Even serum- 

 albumin and serum-globulin possess this property in some degree. 

 All these substances also cause a diminution in the number of 

 leucocytes in the blood owing, in the case of albumose at any rate, 

 to their accumulation in the abdominal vessels, and not to any 

 actual destruction of them. 



It has been lately announced that the adrenal glands have a relation 

 to the coagulation of the blood. Stimulation of the splanchnic nerve, 

 which supplies secretory fibres to the adrenal, greatly hastens coagula- 

 tion, but has no such effect if the adrenal on the corresponding side 

 has been previously removed (Cannon). It is possible that this effect 

 is exerted through the liver, since it is known that one important 

 function of the liver, the regulation of the sugar content of the blood, 

 is intimately dependent upon the adrenal, and is affected by excitation 

 of its splanchnic nerve-supply. 



In certain pathological conditions the normal balance of the factors 

 that make for clotting and prevent it may be upset, and the scales may 

 tip in either direction. In patients suffering from the formation of 

 spontaneous clots in the veins (thrombosis) it is stated that the anti- 

 thrombin in the blood is diminished, the amount of prothrombin being 

 normal. The mere slowing of the blood-stream in conditions where 

 the circulatory mechanism is enfeebled may favour thrombosis. For 

 anything which cripples the circulation, and consequently limits the 

 free interchange between blood and tissues, interferes with the elimina- 

 tion or neutralization of the precursors of thrombin, and with the 

 entrance of the substances that render the fully formed thrombin in- 

 active. This, as well as the injury caused by the ligature, which may 

 favour the passage of thromboplastic substances into the lumen of the 

 occluded vessel, is a possible factor in the formation of the clot 

 on which the surgeon relies for the permanent sealing of ligated 

 vessels. 



In haemophilia, a disease in which the coagulation of the blood is 

 characteristically slow, and in which even slight wounds may occasion 

 . severe or fatal haemorrhage, the thrombogen (prothrombin) has been 

 found deficient in amount, and the injection of normal serum or the 

 transfusion of normal blood has been used with temporary advantage 

 in the treatment of the condition. In certain cases of purpura, how- 

 ever, where haemorrhage also occurs with abnormal ease, no variation 

 from the normal could be detected in the content of either antithrombin 

 or prothrombin (Ho well). Some have supposed that in such conditions 

 the fault is an unnatural fragility of the small vessels rather than a 

 deficiency in the power of the blood to clot, but of this also no actual 

 evidence has been adduced. Another factor on which the promptness 

 and completeness of the sealing of wounded vessels may depend has been 

 recently brought into notice, namely 



The Vaso-Constrictor Property of Shed Blood. It has been shown 

 that when blood is shed and no precautions are taken to prevent 

 clotting, it very quickly develops the power of causing marked 

 constriction of bloodvessels. This can be demonstrated by allow- 

 ing the serum to act on rings cut from arteries (Practical Exercises, 



