112 AEISTOTLE'S HOMCEOMERIA. 



red cells, or erythroblasts, which are concerned in the pro- 

 duction of the red corpuscles of the blood. 



8. Blood, Serum, and the like. — Aristotle paid much 

 attention to these homoeomeria. He gives a great deal of 

 interesting information about the blood, the serum or watery 

 part of it, and the process of coagulation. He says that 

 normally healthy blood contains a sweet juice and is of a red 

 colour, and that blood which is dark in colour, either 

 naturally or as a result of disease, is inferior to that which 

 is of a red colour.* It is true that there is a very small 

 quantity of dextrose in blood, but this is not apparent to the 

 taste, the blood being slightly salt. 



Aristotle believed, as has been stated in Chapter iv., that 

 blood was not an essentially hot liquid, but derived its heat\ 

 from the heart, at least to a large extent. Comparing the 

 blood of Man with that of some other animals, he says that 

 Man has the brightest and thinnest blood, and that the ox 

 and the ass have the darkest and thickest.! The colours of 

 arterial blood in Man, the ox, and apparently the ass, differ 

 very little from one another, and the same is true of the 

 colours of the venous blood. The arterial blood of the 

 pigeon and many other birds is lighter than that of Man or 

 the ox. With respect to Aristotle's statement about the 

 relative consistency of the blood in Man and the ox, it 

 appears from Thackrah's experiments that the blood of the 

 ox is thinner than that of the pig or dog, and not thicker 

 than that of Man.+ Aristotle says that the blood which 

 supplies the brain is small in amount and pure.§ In most 

 animals the supply of blood to the brain is large, but 

 Aristotle's statement is quite in accordance with several 

 statements he makes about the brain, in which, he says, no 

 blood-vessel is to be seen. Further, the blood supplied to 

 the brain in Man and other mammals and in birds is 

 scarcely, if at all, purer than that supplied to other parts. 

 It is true, however, that in the Batrachia, Ophidia, Lacer- 

 tilia, Chelonia, and, to a less extent, the Crocodilia, the 

 structure of the heart and arrangement of the main blood- 

 vessels are such that the purest blood is sent to the brain. 



There are several passages in his works showing that 

 Aristotle noticed differences, or what he thought were 



* H. A. iii. c. 14, s. 1. \ Ibid. iii. c. 14, s. 3. 



I An Inquiry into the Nature and Properties of the Blood, &c., 

 Wright's edition, 1834, pp. 154 and 236. 



§ P. A. ii. c. 7, 6526. 



