Page:The Works of William Harvey (part 1 of 2).djvu/510

 not in act. Precisely as from the same rain plants of every kind increase and grow ; because the moisture which was a like power in reference to all, becomes actually like to each when it is changed into their substances severally : then does it acquire bitterness in rue, sharpness in mustard, sweetness in liquorice, and so on.

He explains, moreover, what parts are engendered before others, and assigns a reason which does not differ from the second basis of Fabricius. " The cause by which, and the cause of this cause, are different ; one is first in generation, the other in essence ;" by which we are to understand that the end is prior in nature and essence to that Avhich happens for the sake of the end ; but that which happens for the sake of the end must be prior in generation. And on this ground Fabricius rightly infers that all those parts which minister to the vegeta- tive principle, are engendered before those that serve the sen- sitive principle, inasmuch as the former is subordinate to the latter.

He subsequently adds the differences of those parts which are made for some special purpose : some parts, for example, are instituted for a purpose by nature, because this purpose en- sues ; and others because they are instruments which the pur- pose employs. The former he designates genitalia, the latter instrumenta. For the end or purpose, he says, in some cases, is posterior, in others prior to that which is its cause. For both the generator and the instruments it uses must exist an- teriorly to that which is engendered by or from them. The parts serving the vegetative principle, therefore, are prior to the parts which are the ministers of sense and motion. But the parts dedicated to motion and sensation are posterior to the motive and sensitive faculties, because they are the instruments which the motive and. sensitive faculties employ. For it is a law of nature that no parts or instruments be produced before there be some use for them, and the faculty be extant which employs them. Thus there is neither any eye nor any motive organ engendered until the brain is produced, and the faculties pre- exist which are to see and to govern motion.

In like manner, as the pulsating vesicles serve as instruments for the motion of the blood, and the heart in its entire struc- ture does the same, (as I have shown in the work on the Mo-