AND THEIR FUNCTIONS. 139 



and resembles blood.* The mytis was probably the liver or 

 digestive gland. The fluid of this, however, is not always like 

 blood, nor is it sweet. In most dibranchiate cephalopods it 

 is reddish brown, but in the lobster and crayfish it is com- 

 monly yellow. In his OsfraJcoderma and Entoma he con- 

 cluded that the part corresponding with the heart of an 

 animal with blood was in a median position,! but in no case 

 does he appear to have located it. 



Aristotle's description of the arrangement of the blood- 

 vessels may now be considered. Eeference may be made to 

 Fig. 8, which is intended to illustrate his description. He 

 points out the difficulties of tracing the arrangement by the 

 methods followed by others, who dissected slaughtered 

 animals from which much of the blood had flowed, or who 

 examined the bodies of very emaciated men. It is very 

 probable that he himself dissected animals which, after 

 having been starved, were killed by strangulation.! 



He was aware of some differences (as has already been 

 pointed out in Chapter ix.) between what are now called 

 arteries and veins, but he had no knowledge of a circulation 

 of the blood. According to him, the blood flowed outwards 

 from the heart and did not return. In the following 

 description, therefore, the phrase " blood-vessel " will be 

 used wherever possible ; it would be misleading to use the 

 words " artery " and " vein." Except where otherwise 

 stated, in the following description of the arrangement of 

 the blood-vessels, according to Aristotle, the passages relied 

 on are from his H. A. iii. cc. ,3 and 4 (Schneider's text). 

 Aristotle says that two blood-vessels arise from the heart, 

 the smaller one, which some call the aorta, lying a little to 

 the left, and the larger one, called the great blood-vessel, 

 lying a little to the right of the spinal column and nearer 

 to the ventral wall than the aorta. The heart is, as it v/ere, 

 a part of these blood-vessels, especially the great blood- 

 vessel, for the parts of this extend above and below the 

 heart, which is between them. The great blood-vessel, he 

 says, is connected with the upper part of the largest 

 chamber, on the right side, then its course is directed back- 

 wards right through the chamber, as if this were a part of 

 the blood-vessel acting as a reservoir. The aorta, on the 

 other hand, arises from the middle chamber, but not in the 



* P. A. iv. c. 5, 6816. f Ihid. iv. c. 5, 6816 and 682a. 



I H. A. iii. c. 3, s. 1. 



