114 AEISTOTLE'S HOMCEOMEEIA. 



It has already been pointed out, in Chapter i., that it is 

 very difficult to decide to what extent Aristotle was indebted 

 to Plato on subjects of this kind, but on the subject of coagu- 

 lation of the blood it is clear that Plato knew the main 

 facts recorded by Aristotle. On the other hand, Aristotle 

 does not seem to have obtained anything from Hippocrates 

 on this subject. When modern writers state, as many have 

 stated, that Aristotle obtained many ideas from Hippocrates, 

 the distinction between the genuine works of Hippocrates 

 and works written by his followers ought to be borne in 

 mind. Some of the Hippocratic treatises were written 

 after the time of Aristotle. 



Blood, Aristotle says, has a watery portion, called ''x^pf* 

 and, in the blood of most animals, there are certain " fibres," 

 called i'vssA Blood does not coagulate when these fibres 

 have been removed from it. I The coagulation of the blood 

 takes place, he says, not in the watery part but in the earthy 

 part, during the evaporation of the watery part.§ Blood, 

 according to him, is composed of earthy and watery parts, 

 and needs a certain amount of water to keep it liquid and 

 also a certain amount of heat, and therefore it can be 

 coagulated by heating so as to evaporate the water and by 

 cooling so as to drive off heat together with watery vapour. |1 

 He believed also that some animals had a hasty temper in 

 consequence of the many "fibres" in their blood, and he 

 explains that the " fibres " are like so many hot embers in 

 the blood, and act like the hot embers of a vapour bath.H 



The above passages show clearly that Aristotle con- 

 sidered that blood had two constituents at least, vu., serum 

 and certain fibres which correspond with what is now called 

 fibrin and is readily separable from blood by beating it with 

 a twig. He gives but little information about the nature of 

 the fibres themselves. It is clear, however, that he believed 

 that they were solid bodies of a hot nature existing in the 

 blood of the living animal. These solid bodies, according to 

 him, constituted the blood clot, when the blood was coagu- 

 lated. His explanation of the process of coagulation by 

 cooling so as to get rid of heat and water does not take 

 account of the fact that the clot forms as a separate mass in 

 a large quantity of serum, only a very small quantity of 

 water passing away during the cooling. That fibrin is 



•:= P. A. ii. c 4, 651a.. f Ibid. ii. c. 4, 6506 ; H. A. iii. c. 6. 



I H. A. iii. c. 6. § P. A. ii. c. 4, 6506. 



II Meteorol iv. c. 7, ss. 10-13. II P. ^. ii. c. 4, 6506 and 651rt. 



