64 ON THE MOTION OF THE BLOOD. 



These valves are not found in some parts ; not in the" 

 brain, heart, lungs, secimdines, nor in the system of 

 the vena portae. 



97. The twigs, or, more properly, the radicles, of the 

 veins, unite into branches, and these again into six 

 principal trunks : viz. into the two cava?, superior and 

 inferior ; and the four trunks of the pulmonary vein (the 

 arteria venosa of the ancients). 



The vena portae is peculiar in this, that, having en- 

 tered into the liver, it ramifies like an artery, and its 

 extreme twigs pass into the radicles of the inferior 

 cava, thus coalescing into a trunk. 



98. That the blood may be properly distributed and 

 circulated through the arteries and veins, nature has 

 provided the heart, * in which the main trunks of all 

 the blood vessels unite, and which is the grand agent 

 and mover of the whole system, supporting the chief 

 of the vital functions with a constant and truly wonder- 

 ful power, from the second or third week after concep- 

 tion to the last moment of existence. 



99. The heart alternately receives and propels the 

 blood. Receiving it from the body by means of the 

 superior and inferior vena cava, and from its own sub- 

 stance through the common valvular -f- orifice of the 

 coronary veins, it conveys that fluid into the anterior 

 sinus and auricle; and thence into the corresponding 

 ventricle, which, as well as the auricle, communicates 



* W. Cowper, Myotomia Refonnata. (Postli.) Lond. 172-1. Fol. max. 

 Tab. xxxvi xl. 



f Casp. Fr. Wolflf on the origin of the large coronary vein, Act. Ac*(t. 

 Sclent. Petropol. 1777. P. i. 



Petr. Tabarram on the same subject, Atti di Siena. Vol. vi. 



