CLASSICAL ANTIQUITY, MIDDLE AGES 19 

 is the Starting-point of the circulation of the blood; the blood flows to it 

 from the rest of the body, and there obtains warm temperature from the 

 left cavity — that is to say, the blood coming from the body is "cold." 

 The left heart-cavity gets warmth from the air through the pulmonary veins. 

 The arteries likewise contain this warm kind of air, called pneuma, which 

 maintains vital action, and they disperse it throughout the body. It is truly 

 remarkable that, in spite of observations made from innumerable dissections 

 and vivisections performed by various research-workers, this primitive 

 butcher's experience of the emptiness of the left heart-chamber and of the 

 arteries should have been maintained up to the final era of the science of 

 antiquity.^ The warmed-up blood is forced from the right cavity of the heart 

 out into the body. In contrast to these primitive conceptions, however, cer- 

 tain of the Hippocratics have had some idea, though a vague one, of the 

 movement of the blood as an actual circulation. 



Of the nervous system the Hippocratic school had, if possible, a still 

 vaguer idea than of the circulation of the blood. The brain was believed to be 

 a gland which segregates water and possesses the function of cooling the 

 blood and collecting mucus out of the body. This mucus is then segregated, 

 together with the water, by a catarrhal affection through the nose. Certain 

 later Hippocratics, however, probably influenced by Democritus, have a more 

 accurate view of the functions of the brain, believing it to be the centre of 

 thought, feeling, and motion. The nerves are invariably confused with the 

 tendons, sometimes also with the veins, and for this reason all ideas of the 

 functions of the nervous system are already ruled out. Certain of the most 

 important cerebral nerves are, however, described and named. The construc- 

 tion of the eye was fairly thoroughly studied; its membranes and fluids, as 

 well as the pupil, were known, but the lens was unknown. Sight was pro- 

 duced as a reflection of the object seen on the pupil. Of the ear the bony laby- 

 rinth, the auditory canal, and the tympanum were known. The urogenital 

 apparatus is described in its main features; regarding fertilization there 

 existed then, as indeed throughout antiquity, extraordinarily fantastic ideas. 



With zoology proper the Hippocratics naturally had little cause to con- 

 cern themselves. Nevertheless, there exists a treatise On Diet, in which there 

 are enumerated fifty-two different edible animals, arranged on a certain defi- 

 nite system; first quadrupeds, tame and wild, birds, fish of several kinds, in- 

 cluding coast-fish, mud-fish, river-fish, mussels, and crayfish. This so-called 

 Coan animal system has the advantage of differentiating between various cate- 

 gories of living creatures — a first primitive attempt at proper systematization. 



3 This idea possessed, it is true, the sanctity of religion; in sacrificial animals the arteries 

 were naturally empty, and the interior parts of these animals were examined with a view to 

 basing on them prophecies of the future. To deny the results of such examinations would of 

 course have involved wounding time-sanctioned religious susceptibilities. 



