AND THEIR FUNCTIONS. 159 



mesentery, and extending, like roots, between the intestine 

 and the chief blood-vessels.* 



The oesophagus opens into the stomach, he says, after 

 passing through the diaphragm, and is extensible both in 

 length and diameter ; the human stomach, he adds, is like 

 that of a dog, for it is not much wider than the intestine and 

 looks like a wide part of the intestine.! The omentum, he 

 says, is a fatty membrane attached along the middle of the 

 stomach where there is, as it were, a seam of that organ, 

 and the mesentery is a fatty membrane lying above or 

 dorsally to the intestines.! The omentum, mesentery, 

 and diaphragm are present, he says, in all animals with 

 blood. § 



Aristotle evidently never saw a human stomach, the 

 maximum sectional area of which is decidedly greater than 

 that of the intestines, while its form is such as to distinguish 

 it at once from them. The omentum, by which he probably 

 meant the great omentum, is present in mammals only, but 

 the mesentery is found in most, if not all, vertebrates. The 

 w^ord used by Aristotle to denote the diaphragm is diazo77ia 

 or sometimes phrenes or liypozoma, but each is sometimes 

 used in a puzzling sense, for birds, reptiles, fishes, and even 

 some invertebrates are said to have a diazoma or hypozoma. 

 The meaning of these words can be ascertained, in such 

 cases, only by reference to the context, and, in many 

 cases, it is evident that they refer merely to a region of an 

 animal's body, and not to a membrane or the like serving as 

 a partition. Aristotle's ideas about the diazoma or hypo- 

 zoma, like those of Plato, are connected with his ideas about 

 the soul. In P. A. iii. c. 10, 6726, he says that all animals 

 with blood have a diazoma, sometimes called phrenes, which 

 is necessary for dividing the region of the nobler from that 

 of the animal passions. 



He was aware that the stomachs of various animals vary 

 greatly in size and shape, and in the positions of the inlet of 

 the oesophagus, il but his most interesting description is that 

 relating to the stomach of a ruminant, such description 

 being so accurate as to suggest that he dissected the 

 stomach of one of these animals. According to him, it has 

 four chambers of the following kind: — "Commencing at 



- P. A. iv. c. 4, 678a. \ H. A. i. c. 13, s. 9. 



I Ibid. i. c. 13, s. 10, iii. c. 11, s. 2. ^ P. A. iv. c. 1, 6766. 



II H. A. ii. c. 12, s. 7; P. A. iii. c. 14, 675a. 



