300 THE BLOOD. 



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 dis- 

 solved 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 circulation. 

 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 uninjured 

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

 tions 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 oanula 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 

 to FREUND 3 it is this adhesion between the blood and a foreign substance 



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; Brucke, Virchow's Arch., 12, 



3 Freund, Wien. med. Jahrb., 1886; Haycraft and Carlier, Journ. of Anat. and 

 Physiol., 22. 



