414 BLOOD AND LYMPH. 



substance, glutolin, which is present in the blood and is usually precipitated 

 together with the paraglobulin. A number of observers have ,noted the ex- 

 istence in blood of a proteid not coagulated by heat. By some authors this 

 has been described as a peptone or an albumose (Langstein), by others as an 

 ovomucoid (Zanetti) and by others still (Chabrie) as a peculiar proteid for which 

 the name albumon has been proposed. By others still this non-coagulable 

 proteid obtained from serum or plasma has been explained as an artificial 

 product arising from the globulins of the blood during the process of remov- 

 ing the coagulable proteids by heating. So, too, nucleoproteid substances have 

 been described in the blood-serum by several observers, most recently by 

 Freund and Joachim. It is quite possible, however, that the substance des- 

 cribed as nucleoproteid is in reality a mixture or combination of lecithin and 

 proteid. All the proteids when precipitated from the blood carry down with 

 them some lecithin, and will therefore show a reaction for phosphorus. It 

 can be shown that the phosphorus present is, in most cases at least, remov- 

 able by boiling with alcohol, and there is at present no entirely satisfactory 

 proof that nucleo-albumins exist in the blood. 



Coagulation of Blood. One of the most striking properties of 

 blood is its power of clotting or coagulating shortly after it escapes 

 from the blood-vessels. The general changes in the blood during 

 this process are easily followed. At first perfectly fluid, in a few 

 minutes it becomes viscous and then sets into a soft jelly which 

 quickly becomes firmer, so that the vessel containing it may be 

 inverted without spilling the blood. The clot continues to grow 

 more compact and gradually shrinks in volume, pressing out a 

 smaller or larger quantity of a clear, faintly yellow liquid to which 

 the name blood-serum is given. The essential part of the clot is the 

 fibrin. Fibrin is an insoluble proteid not found in normal blood. 

 In shed blood, and under certain conditions in blood while still in the 

 blood-vessels, this fibrin is formed from the soluble fibrinogen. 

 The deposition of the fibrin is peculiar. It is precipitated, if the 

 word may be used, in the form of an exceedingly fine network of 

 delicate threads that permeate the whole mass of the blood and give 

 the clot its jelly-like character. The shrinking of the threads 

 causes the subsequent contraction of the clot. If the blood has not 

 been disturbed during the act of clotting, the red corpuscles are 

 caught in the fine fibrin meshwork, and as the clot shrinks these 

 corpuscles are held more firmly, only the clear liquid of the blood 

 being squeezed out, so that it is possible to get specimens of serum 

 containing few or no red corpuscles. The leucocytes, on the con- 

 trary, although they are also caught at first in the forming 

 meshwork of fibrin, may readily pass out into the serum in the later 

 stages of clotting, on account of their power of making ameboid 

 movements. If the blood has been agitated during the process of 

 clotting, the delicate network will be broken in places and the serum 

 will be more or less bloody that is, it will contain numerous red 

 corpuscles. If during the time of clotting the blood is vigorously 

 whipped with a bundle of fine rods, all the fibrin is deposited 

 as a stringy mass upon the whip, and the remaining liquid part 



