CHAPTER XVIII. 



BLOOD, RESPIRATION, CIRCULATION AND ITS DISTURBANCES. 



Blood. 



(See also Chapter XIV, The Distribution of Water in the Organism.) 



THE blood consists of a fluid, the plasma, and the formed elements, 

 the blood corpuscles. 



Plasma. 



In a short time after the blood leaves the body it coagulates 

 spontaneously. It separates into two components; one a yellowish 

 fluid, the serum, and the jelly-like clot, the fibrin, which has enmeshed 

 the blood corpuscles and has undergone shrinking during coagulation. 

 If the blood is beaten or shaken with a rough surface (wood or steel 

 shavings) after it has left the vein, it clots at once and the fibrin 

 separates immediately as an irreversible fibrous mass which may be 

 completely cleansed of the adherent constituents of the blood by 

 washing it with water. Recently colloid-chemical explanations asso- 

 ciated with the names K. SPIRO and ELLINGER, NOLF, RETTGER, 

 and HEKMA have received more support. Fibrin occurs in the blood 

 as fluid fibrinalbuminate (fibrinogen) which is normally characterized 

 by being coagulated by dilute salt solutions and serum, so that 

 something must exist in the blood which prevents coagulation in the 

 vessels. We possess no knowledge as to what this "something" is. 

 [HOWELL has recently separated this substance antiprothrombin. See 

 HARVEY Lectures, 1916-1917 to be published. Tr.] Certain aspects 

 may be indicated which help the solution of the problem. Coagula- 

 tion occurs when the blood leaves the closed vascular system, and 

 comes into contact with other surfaces which it moistens. If blood is 

 collected in oil or vaseline, it remains fluid many hours and may even 

 be beaten with a thoroughly greased glass rod without clotting. 

 Shed blood may be centrifuged in paraffined vessels and a plasma 

 may be thus obtained which remains fluid, provided the suggested 

 precautions are employed. Such plasma clots when a glass rod which 

 it moistens is introduced. It is not known whether or not the inter- 

 face blood/gas plays any part in clotting. 



H. ISCOVESCO is of the opinion that the electric charge of the 

 vessel wall plays an important part in the coagulation of fibrin; in 



299 



