22 PHYSIOLOGY FOR NURSES 



course of the lymphatic channels are found the lym- 

 phatic glands, which act as niters, attempting to prevent 

 the entrance of bacteria or toxins into the circulation. 

 The "waxen kernels" are lymphatic glands that have 

 become inflamed and swollen as the result of the action 

 of some toxic agent. 



Coagulation. The clotting or coagulation of the 

 blood is nature 's way of stopping hemorrhage and where 

 there is derangement of the process, serious or even 

 fatal hemorrhage may occur from an apparently trivial 

 wound. A substance known as prothrombin and salts of 

 calcium is found in the blood. If calcium acts on pro- 

 thrombin, it converts the latter into thrombin and throm- 

 bin causes fibrinog'en, a soluble protein of the blood 

 plasma, to assume an insoluble form, known, as fibrin, 

 this latter constituting the clot, enclosing the red corpus- 

 cles in its meshes. The white cells possess the power of 

 movement, so they are not included in the clot to any 

 considerable extent. That blood does not normally clot 

 in the vessels, is explained by the presence of a substance 

 known as antithrombin, which prevents the action of the 

 calcium salts on the prothrombin. When tissues are 

 wounded, another substance, known as kephalin or 

 "thromboplastic'' substance, neutralizes the antithrom- 

 bin and allows the conversion of prothrombin into active 

 thrombin. If blood is obtained by puncturing a vein and 

 drawing the blood into a perfectly clean syringe, contact 

 with wounded tissue is prevented and coagulation is de- 

 layed, because the thromboplastic substance is not de- 

 rived from passing over wounded tissue. Clotting will oc- 

 cur, however, because the platelets will gradually dis- 

 integrate and furnish the requisite thromboplastic ma- 

 terial. The hemorrhagic diseases which have been men- 

 tioned, are accompanied by a marked increase in the 



