History and Progress of Comparative Anatomy. 51 



tract it appears that Servet maintains the existence of a vital 

 spirit, which is seated in the heart and the arteries, and in the for- 

 mation of the spirit and its combination with the blood, he re- 

 presents life essentially to consist. The vital spirit, he continues, 

 which is thin, of a yellow colour, elaborated by heat, originates in 

 the left ventricle, but is chiefly completed m the lungs by combi- 

 nation of the inspired air with the elaborated refined blood which 

 the right ventricle conveys to the left. This communication, how- 

 ever, he argues, does not take place through the wall of the 

 heart, which is impervious ; but by an ingenious contrivance the 

 thin blood is conveyed from the right ventricle of the heart by 

 a long channel through the lungs, where it is prepared, assumes 

 a yellow colour, and is transferred from the arterious vein (the 

 pulmonary artery) into the venous artery (the pulmonary veins). 

 Then, after being mixed with inspired air, and purified by ex- 

 piration from fuligo, it is attracted by the left ventricle, from 

 which, he afterwards remarks, it is distributed in the form of 

 vital spirit through the arteries. This course of the blood, he 

 concludes, is demonstrated by two facts, 1*^, The communica- 

 tion of the arterious vein and venous artery in the lungs ; and, 

 9,d, By the size of the arterious vein, which would not be so 

 considerable merely for nourishing the lungs. 



It deserves remark, that this contains not only the eleinents 



ex facta in pulmone conunixtioiie inspirati aeris cum elaboralo subtili san- 

 guine, quem dexter ventriculus sinistro communicat. Fit autem communi- 

 catio haec, non per parietem cordis medium, ut vulgo creditur, sed magno ar- 

 tificio a dextro cordis ventriculo, longo per pulmones ductu agitatur sanguis 

 subtilis ; a pulmonibus praeparatur, flavus efficitur, et a vena arteriosa in ar- 

 teriam venosam transfunditur. Deinde in ipsa arteria venosa, inspirato aeri 

 miscetur, et exsj)iratione a fuligipe expurgatuv ; atque ita tandem a sinistro 

 cordis ventriculo totum niixtum per diastolen atlrahitur, apta supellex, ut 

 fiat spiritus vitalis. Quod ita per pulmones fiat communicatio et prseparatio, 

 docet conjunctio varia, et communicatio venae arteriosae cum arteria venosa in 

 pulmonibus. Confirmat hoc magnitude insignis venae arteriosae, quae nee talis 

 nee tanta facta esset, nee tantam a corde ipso vim purissimi sanguinis in pul- 

 mones emitteret, ob solum eorum nutrimentum ; nee cor pulmonibus hac ra- 

 tione serviret, cum praesertim antea in embryone solerent pulmones ipsi ali- 

 unde nutriri, ob membranulas illas seu valvulas cordis, usque ad horum nati- 

 vitatem ; ut docet Galenus, &c. Itaque ille spiritus a sinistro cordis ventri. 

 culo arterias tolius corporis deinde transfunditur, ita ut qui tenuior est, 

 superiora petit, ubi magis elaboratur, praecipue in plexu retiformi, sub basi 

 cerebri site, ubi ex vitali fieri incipit animalis, ad propriam vationalis aniniae 

 rationem accedens."— BiWworanAie Instrtictive, vol. i. p. 421. 



d2 



