THE BLOOD. 89 



and entire blood-vessels exert upon it. These views are derived 

 from the observations of many investigators. From the observa- 

 tions of HEWSON, LISTER, and FREDERICQ it is known that when 

 a vein full of blood is tied at the two ends and removed from the 

 body, the blood may remain fluid for a long time. BRUCKE allowed 

 the heart removed from a tortoise to beat at 0C., 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 coagu- 

 lates, 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 has 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 has 

 been confirmed later by HAYCRAFT and CARLIER. FREUND found 

 on further investigating 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, it is this adhesion between the blood or between its 

 form-elements and a foreign substance and the diseased walls 

 of the vessels also act as such that gives the impulse towards 

 coagulation, while the lack of adhesion prevents the blood from 

 coagulating. This adhesion of the form-elements of the blood 

 to certain foreign substances seems to induce changes which 

 apparently stand in a certain relationship to the coagulation of 

 the blood. 



That view of the coagulation of the blood which, with a few 

 modifications, is accepted by most investigators is the theory pro- 

 posed by ALEXANDER SCHMIDT and the DORP AT SCHOOL. Accord- 

 ing to ALEX. SCHMIDT, who of all investigators has done most to 

 elucidate this subject, an abundant destruction of the colorless blood- 

 corpuscles takes place in coagulation, and from this not only the 

 fibrin ferment results, but also serum globulin and fibrinogen, which 



