COAGULATION OF THE BLOOD. 313 



infusion also acts in the same way on blood just drawn. Coagulation 

 is also hindered by snake poison (cobra-poison), and bacterial toxines. 

 The coagulation may be facilitated by raising the temperature; by con- 

 tact with foreign bodies, to which the blood adheres; by stirring or beat- 

 ing it; by admission of air; by diluting with very small amounts of 

 water; by the addition of platinum-black or finely powdered carbon; 

 by the addition of laky blood, which does not act by the presence of 

 dissolved blood-coloring matters, but by the stromata of the blood-corpus- 

 cles; and also by the addition of the leucocytes from the lymphatic 

 glands, or of a watery saline extract of the lymphatic glands, testicles, or 

 thymus and various other organs (DELEZENNE, WRIGHT, ARTHUS/ and 

 others). 



An important question to answer is why the blood remains fluid 

 in the circulation, while it quickly coagulates when it leaves the circula- 

 tion. The reason why blood coagulates on leaving the body is therefore 

 to be sought for in the influence which the walls of the living and unin- 

 jured blood-vessels exert upon it. These views are derived from the 

 observations of many investigators. From the observations of HEWSON, 

 LISTER, and FREDERICQ it is known that when a vein full of blood is 

 ligatured at the two ends and removed from the body, the blood may remain 

 fluid for a long time. BRUCKE 2 allowed the heart removed from a tortoise 

 to beat at C., and found that the blood remained uncoagulated for 

 some days. The blood from another heart quickly coagulated when 

 collected over mercury. In a dead heart, as also in a dead blood-vessel, 

 the blood soon coagulates, and also when the walls of the vessel are changed 

 by pathological processes. 



What then is the influence which the walls of the vessels exert on 

 the liquidity of the circulating blood? FREUND found that the blood 

 remains fluid when collected by means of a greased canula under oil or 

 in a vessel smeared with vaseline. If the blood collected in a greased 

 vessel be beaten with a glass rod previously oiled, it does not coagulate, 

 but it quickly coagulates on beating it with an unoiled glass rod or when 

 it is poured into a vessel not greased. The non-coagulability of blood 

 collected under oil was confirmed later by HAYCRAFT and CARLIER. 

 FREUND found on further investigation that the evaporation of the 

 upper layers of blood or their contamination with small quantities of dust 

 causes a coagulation even in a vessel treated with vaseline. According 



1 Delezenne, Arch, de Physiol. (5), 8; Wright, Journ. of Physiol., 28; Arthus, 

 Journ. de Physiol. et Pathol., 4. 



2 Hewson's works, edited by Gulliver, London, 1876, cited from Gamgee, Text- 

 book of Physiol. Chem., 1, 1880; Lister, cited from Gamgee, ibid.- Fredericq, Recher- 

 ches sur la constitution du plasma sanguin, Gand, 1878; Briicke, Virchow's Arch. 12. 



