82 MOTION OF THE 



which is because they are present before the heart [the ventri- 

 cular portion] makes its appearance or suffices for its office even 

 when it has appeared, and they therefore have, as it were, the duty 

 of the whole heart committed to them, as has already been de- 

 monstrated. 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 ques- 

 tion 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 internately 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 con- 

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

 perfection in each. These points will be found elsewhere con- 

 firmed by numerous observations on the formation of the foetus. 



Finally, it was not without good grounds that Hippocrates, 

 in his book, e De Corde/ intitles it a muscle ; as its action is 

 the same, so is its function, viz., to contract 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 fibres 

 and its general structure. All anatomists admit with Galen 

 that the body of the heart is made up of various courses of 

 fibres running straight, obliquely, and transversely, with refer- 

 ence to one another ; but in a heart which has been boiled the 

 arrangement of the fibres is seen to be different : all the fibres 

 in the parietes and septum are circular, as in the sphincters ; 



