AND THEIR FUNCTIONS. 137 



According to Aristotle, the heart has three chambers, 

 the largest being on the right side, the smallest on the left 

 side, and the one of intermediate size being between the 

 other two ; the two smaller chambers are much smaller than 

 the largest, and, while all the chambers are readily seen in 

 large animals, only two or even one can be seen in smaller 

 animals,* 



Apparently, the largest or right chamber is the right 

 ventricle, together with the right auricle, the smallest or 

 left is the left auricle, and the intermediate chamber is the 

 left ventricle. Aristotle's description of the chambers was 

 probably based on dissections of this organ in some mammal 

 or mammals. He does not say what animals he dissected 

 for this purpose, but, for several reasons, more especially 

 because he was acquainted with the existence of a bone in 

 its heart, it is not unlikely that the ox was one of them. If 

 so, it would not be surprising that he considered the right 

 ventricle and right auricle to form one chamber which, as 

 he says, was much larger than either of the other chambers. 



When the heart of an ox, freed from its firmly adherent 

 masses of suet, is carefully dissected and placed so as to 

 allow anyone to look down into its auricles and ventricles, 

 the passage from the right auricle to the right ventricle is 

 seen to be much more gradual than the passage from the left 

 auricle to the left ventricle, between which there is a well- 

 marked annular ridge. Then, again, the auriculo-ventricular 

 valves between the right auricle and right ventricle lie very 

 close to the chamber walls, and no well-marked boundary is 

 seen between the right auricle and right ventricle. 



It should be mentioned that, instead of the view 

 expressd above, Aubert and Wimmer considered the two 

 auricles to form Aristotle's largest chamber, Frantzius con- 

 sidered this to be the right auricle, and Dr. Ogle the right 

 ventricle. 



Aristotle says that there are sinews in the chambers of 

 the heart,! but in H. A. iii. c. 5, s. 1, he says that the 

 sinews are in its largest chamber. It is clear that the 

 chordae tendineae are meant. These occur, as is well known, 

 in both ventricles. 



In H. A. i. c. 14, s. 1, the pericardium seems to be 

 referred to, for it is stated that the heart has a thick, fatty 

 membrane, by which it is attached to the great blood-vessel 



* H. A. i. c. 14, ss. 1 and 2, iii. c. 3, s. 2 ; P. A. iii. c. 4, 6666. 

 f H. A. i. c. 14, s. 1 ; P. A. iii. c. 4, 6666. 



