8o FATHERS OF BIOLOGY. 



omentum and its connections with the stomach, the 

 spleen, and the colon ; and he enunciated the first correct 

 views of the structure of the pylorus, noticing at the 

 same time the small size of the csecal appendix in man. 

 His account of the anatomy of the brain is fuller than 

 that of any of his predecessors, but he does not appear 

 to have well understood the inferior recesses, and his 

 description of the nerves is confused by regarding the 

 optic as the first pair, the third as the fifth, and the fifth 

 as the seventh. The ancients believed the optic nerve 

 to be hollow for the conveyance of the visual spirit, but 

 Vesalius showed that no such tube existed. He observed 

 the elevation and depression of the brain during respira- 

 tion, but being ignorant of the circulation of the blood, 

 he wrongly explained the phenomenon. 



Exclusively an anatomist, he makes but brief references 

 in his great work to the functions of the organs which he 

 describes. Where he differs from Galen on these matters 

 he does so apologetically. He follows him in regarding 

 the heart as the seat of the emotions and passions the 

 hottest of all the viscera and source of heat of the whole 

 body ; although he does not, as Aristotle did, look upon 

 the heart as giving rise to the nerves. He considers the 

 heart to be in ceaseless motion, alternately dilating and 

 contracting, but the diastole is in his opinion the in- 

 fluential act of the organ. He knows that eminences or 

 projections are present in the veins, and indeed speaks of 



