104 Motion of the 



have, as it were, the duty of the whole heart committed 

 to them, as has already been demonstrated. But what 

 I have observed in the formation of the foetus as 

 before remarked (and Aristotle had already confirmed 

 all in studying the incubated egg,) throws the greatest 

 light and likelihood upon the point. Whilst the foetus 

 is yet in the guise of a soft worm, or, as is commonly 

 said, in the milk, there is a mere bloody point or 

 pulsating vesicle, a portion apparently of the umbilical 

 vein, dilated at its commencement or base ; by and by, 

 when the outline of the foetus is distinctly indicated, 

 and it begins to have greater bodily consistence, the 

 vesicle in question having become more fleshy and 

 stronger, and changed its position, passes into the 

 auricles, over or upon which the body of the heart 

 begins to sprout, though as yet it apparently performs 

 no duty ; but when the foetus is farther advanced, when 

 the bones can be distinguished from the soft parts, and 

 movements take place, then it has also a heart inter- 

 nately which pulsates, and, as I have said, throws 

 blood by either ventricle from the vena cava into the 

 arteries. 



Thus nature, ever perfect and divine, doing nothing 

 in vain, has neither given a heart where it was not 

 required, nor produced it before its office had become 

 necessary ; but by the same stages in the development 

 of every animal, passing through the constitutions of 

 all, as I may say (ovum, worm, foetus), it acquires 

 perfection in each. These points will be found else- 

 where confirmed by numerous observations on the 

 formation of the foetus. 



Finally, it was not without good grounds that Hippo- 

 crates, in his book, " De Corde," intitles it a muscle ; as 

 its action is the same, so is its function, viz. to con- 

 tract and move something else, in this case, the charge 

 of blood. 



Farther, as in muscles at large, so can we infer the 

 action and use of the heart from the arrangement of its 



