MALPIGHI 151 



lie was deeply impressed with what he took to be 

 the important truth that Nature is one, and that the 

 same purpose guides her operations in all things. 



In 1671 the Cartesian principle that investigation 

 must proceed from the simple to the complex (a principle 

 which often passes unobserved into the dangerous shape 

 of proceeding from the general to the particular) was 

 prevalent. It led Grew astray, and either this or some 

 older form of the same doctrine had its eflfect upon 

 Malpighi also. He supposed that complex structures 

 can only be mastered by first mastering the simpler 

 ones upon which they depend, or from which they 

 are derived. The study of plants ought, he thought, to 

 precede that of animals, the study of minerals to precede 

 that of plants. It was impossible for him to foresee that 

 minerals could not be studied to much purpose until 

 chemistry and optics were far more advanced than they 

 were in 1671, but one would have thought that the 

 discovery of the circulation of the blood, in which he 

 had a share, might have opened his eyes to the im- 

 portance of opportunity and a definite practical purpose, 

 things which have as much to do with the order of 

 investigation as relative simplicity. The vascular 

 mechanism was by no means a simple thing, such as 

 on the Cartesian principle should have been taken in 

 hand early, but men felt how immensely important it 

 was that the course of the circulation should be properly 

 understood, and they found, by a piece of good fortune, 

 that this question could be decided without wide 

 or accurate knowledge of physiology at large, or even of 

 the physiology of the vascular system. 



The maxim which should guide our work is not from 

 the simple to the complex, nor yet, as some philosophers 

 have taught, ^om the more needful to the less needful, 



