392 ON GENERATION. 



EXERCISE THE FIFTY-THIRD. 



Of the inferences deducible from the course of the umbilical 

 vessels in the egg. 



We find the blood formed in the egg and embryo before 

 any other part ; and almost at the same moment appear its 

 receptacles, the veins and the vesicula pulsans. Wherefore, if 

 we regard the punctum saliens as the heart, and this along 

 with the blood and the veins as constituting one and the same 

 organ, conspicuous in the very commencement of the embryo, 

 although we should admit that the proper substance of the heart 

 was deposited subsequently, still we should be ready to admit 

 with Aristotle that the heart (an organ made up of ventricles, 

 auricles, vessels, and blood) was in truth the principal and pri- 

 mogenate part of the body, its own prime and essential element 

 having been the blood, both in the order of nature and of ge- 

 netic production. 



The parts that in generation succeed the blood are the veins, 

 for the blood is necessarily inclosed and contained in vessels ; 

 so that, as Aristotle observes, we find two meatus venales even 

 from the very first, which canals, as we have shown in our his- 

 tory, afterwards constitute the umbilical vessels. It seems ne- 

 cessary, therefore, to say something here of the situation and 

 course of these vessels. 



In the first place, then, it is to be observed that all the ar- 

 teries and veins have their origin from the heart, and are as it 

 were appendices or parts added to the central organ. If there- 

 fore you carefully examine the embryo of the human subject, 

 or one of the lower animals, and having divided the vena cava 

 between the right auricle and the diaphragm, look into it up- 

 wards or towards the heart, you will perceive three foramina, 

 the largest and most posterior of which tending to the spine is 

 the vena cava; the anterior and lesser proceeds to the root and 

 trunk of the umbilical vessels ; the third and least of all enters 

 the liver and is the origin and trunk of all the ramifications 

 distributed to the convexity of that organ. Whence it clearly 



