66 Greek Biology 



great ability and industry, and knew well the value of the 

 experimental way. Yet he was a somewhat windy philosopher 

 and, priding himself on his philosophic powers, did not hesitate 

 to draw conclusions from evidence which was by no means 

 always adequate. The physiological system that he thus suc- 

 ceeded in building up we may now briefly consider (fig. n). 



The basic principle of life, in the Galenic physiology, is 

 a spirit, anima or pneuma, drawn from the general world-soul 

 in the act of respiration. It enters the body through the 

 rough artery (rpa^la apTr]pia 9 arteria aspera of mediaeval 

 notation), the organ known to our nomenclature as the trachea. 

 From this trachea the pneuma passes to the lung and then, 

 through the vein-like artery (aprripia $Ae/3w?79, arteria venalis 

 of mediaeval writers, the pulmonary vein of our nomenclature), 

 to the left ventricle. Here it will be best to leave it for a 

 moment and trace the vascular system along a different route. 



Ingested food, passing down the alimentary tract, was 

 absorbed as chyle from the intestine, collected by the portal 

 vessel, and conveyed by it to the liver. That organ, the site 

 of the innate heat in Galen's view, had the power of elaborating 

 the chyle into venous blood and of imbuing it with a spirit 

 or pneuma which is innate in all living substance, so long as 

 it remains alive, the natural spirits (irv^v^a tyva-iKov, spiritus 

 nctturalis of the mediaevals). Charged with this, and also with 

 the nutritive material derived from the food, the venous blood 

 is distributed by the liver through the veins which arise from 

 it in the same way as the arteries from the heart. These veins 

 carry nourishment and natural spirits to all parts of the body. 

 I e cur jons venarum^ the liver as the source of the veins, remained 

 through the centuries the watchword of the Galenic physiology. 

 The blood was held to ebb and flow continuously in the veins 

 during life. 



Now from the liver arose one great vessel, the hepatic vein, 

 from division of which the others were held to come off as 



