150 THE HISTORY OF BIOLOGY 



perform actions which indicate a conscious intelligence is a problem which 

 causes the author considerable difficulty; true reason cannot exist in animals, 

 for then they would soon come to resemble man and would, moreover, be 

 immortal; it must therefore be the material vital spirit that, either instinc- 

 tively or mechanically, directs their actions. In endeavouring to apply this 

 theory Willis becomes involved in a maze of speculations that it would be 

 hopeless, and indeed would take too long, to follow in all the subtleties to 

 which they give rise; the numerous learned authorities whom he quotes 

 merely give additional confirmation of the state of helpless confusion into 

 which psycho-physiological speculation had drifted ever since it left behind 

 it the safe harbour of Aristoteleanism. When a scientist of Willis's rank can 

 seriously discuss the question whether the vital spirit can be compared with 

 spiritus vini or hartshorn oil, it is easy to realize to what hopeless lengths 

 the natural-scientific speculation of that age could go. Nevertheless, there 

 were even at that time students of nature who applied with far more sub- 

 stantial results the newly-discovered exact method of research in the sphere 

 of biology. Examples will be given in the next section of this chapter; first, 

 however, we may give one more example of radical anatomical research dur- 

 ing this epoch. 



Raymond Vieussens was born in 1641, of a military family; he devoted 

 himself to medical studies at Montpellier and after having graduated became 

 a doctor at a hospital there. He paid specially keen attention to the study of 

 the structure of the nervous system and after many years of preparatory work 

 published his great Neurologis universalis in 1685. This brought him immediate 

 fame. He was summoned to the court in Paris and was for a time physician 

 there, but afterwards returned to his old post, which he retained until his 

 death, in 171 5. His description of the nervous system is remarkable for its 

 unprecedented accuracy and completeness in its anatomical details; for us it 

 is of special interest as representing the foundation upon which Swedenborg 

 based his ingenious speculations upon the connexions of the nervous system, 

 which Vieussens studied and illustrated with great exactitude. Unfortu- 

 nately he, too, became involved, with but little success, in physiological 

 speculations upon the "spiritu/' of the nervous system, which he believes to 

 be secreted in the brain from the blood circulating through it to the latter, 

 as well as upon a "spirifus nitro-aerius," contained in the blood itself; a kind 

 of acid component thereof, which is drawn from the air and from the con- 

 stituents of food. As a result of these ideas he became involved in a tedious 

 controversy. He also brought out a couple of anatomical works on the heart 

 and the vascular system, but they are of less value than his neurology. 



