n] Circulation of the Blood. 39 



• out chiefly for the sake of the remaining vessel, namely, the 

 "vein-like artery which seizes upon the air in the lungs and 

 " carries it to the heart, the same forsooth being drawn through 

 M them by the heart. It is thus reasonable to suppose that the 

 " lungs exist for the sake of the vein-like artery, the use of 

 " which is that the air may conveniently reach the heart ; for 

 "otherwise the air would be drawn into the cavity of the 

 "thorax and would never reach the heart did not the heart 

 "extend its vein-like artery from its left sinus right up into 

 " the lungs." 



And in his Epilogus he thus sums up : 



" In breathing, Nature puts before herself mainly a double 

 " goal, the generation of the animal spirits, and the regulation and 

 " conservation of the heat of the heart. The heat is maintained 

 " and regulated by the supply of material, by refrigeration, and 

 "by getting rid of superfluous residues. All these things are 

 " brought about by means of the air taken into the body, 

 "whence the necessity of breathing. This breathing is the 

 "bringing in of air by which spirit is carried inwards and 

 " outwards through the mouth, and is divided into inspiration 

 "and expiration. In inspiration air enters the lungs and the 

 " heart for the sake of the supply of material and of refrigera- 

 " tion ; in expiration, on the other hand, the air issues for the 

 " sake of getting rid of superfluous residues. The air enters by 

 " being drawn in, it issues by being driven out ; it is drawn 

 "in, not by any occult virtues or influences, but only by the 

 " principle that a vacuum must be filled up." 



In spite of many clear views as to the mechanics of respira- 

 tion, he holds that the air is carried to the heart by the 

 vein-like artery, and much of his work is taken up in a long 

 discussion as to the exact way in which the air thus entering 

 affects on the one hand the generation of the vital spirits, and 

 on the other hand the innate heat of the heart. 



" If all this belongs to the innate heat of the heart which 

 " burns as with a flame, it must in any case be maintained that 

 " the whole business of maintaining and regulating that heat 

 " consists in the first place of providing material (for the flame), 

 " then of ventilation, then of moderate refrigeration, and lastly 



