68 



111. 4. 



sistent with reason. For the blood is conveyed into the vessels 

 from the heart, but none passes into the heart from without. 

 For in itself it constitutes the origin and fountain, or primary- 

 receptacle, of the blood. It is, however, from dissections and 

 from observations on the process of development that the truth 

 of these statements receives its clearest demonstration. For the 

 heart is the first of all the parts to be formed ; and no sooner 

 is it formed than it contains blood. Moreover the motions of 

 pain and pleasure,^^ and generally of all sensation, plainly start 

 from the heart, and find in it their ultimate termination. This, 

 indeed, reason would lead us to expect. For the starting-point 

 must, whenever possible, be one ; and, of all places, the best 

 suited for a starting-point is the centre. For the centre is one, 

 and is equally or almost equally within reach of every part. 

 Again, as neither the blood itself, nor yet any part which is 

 bloodless, is endowed with sensation, it is plain that that part 

 which first has blood, and which holds it as it were in a receptacle, 

 must be the primary source of sensation.'* And that this part is 

 the heart is not only a rational inference, but is also evident to 

 the senses. For no sooner is the embryo formed, than its heart 

 is seen in motion like a living creature, and this before any 

 of the other parts, as though it constituted the starting-point 

 of life in all animals that have blood. A further evidence of 

 the truth of what has been stated is the fact that no sanguineous 

 animal is without a heart. For the primary source of blood must 

 of necessity be present in them all. It is true that sanguineous 

 animals not only have a heart but also invariably have a liver. 

 But no one could ever deem the liver to be the primary organ 

 either of the whole body or of the blood.''' For the position in 

 which it is placed is far from being that of a primary or dominating 

 part ; and moreover in the most perfectly finished animals there 

 is another part, the spleen, which as it were counterbalances it.'^ 

 Still further, the liver contains no spacious receptacle in its 

 substance, as does the heart, but has its blood in a vessel like 

 all the other viscera. The vessel moreover extends through it, and 

 no vessel whatsoever originates in it ; for it is from the heart 

 that all the vessels take their rise. Since then one or other of 

 these two parts must be the central source, and since it is not 

 the liver which is such, it follows of necessity that it is the 

 heart which is the source of the blood, as also the primary 

 666 a. 



