148 Sylvius and his Pupils. [lect. 



1668, whose name is perpetuated in his sal mirabile, Glauber's 

 salt, sodium sulphate, and who though he made no marked 

 contribution to physiology, largely increased the chemical 

 knowledge of his time, Sylvius devoted much energy to the 

 study of salts. He probably owed much to Glauber, who 

 appears to have been one of the first to lay hold of the idea of 

 chemical affinity. But in any case Sylvius learnt to recognize 

 the nature of many salts as the result of a union of acids with 

 bases. He was the first to prove the presence of volatile alkalis 

 in plants. And it is perhaps mainly by the increased knowledge 

 of the various salts, and their composition, that his chemical 

 science is in advance of that of van Helmont, who died just 

 about or rather just before the time when Sylvius began to write. 

 If he was like van Helmont in being a chemist and in 

 looking at the phenomena of life from a chemical point of 

 view, and if he followed van Helmont in explaining many of 

 the events of the living body as due to fermentative processes, 

 successor, and in this respect may be regarded as van Helmont's 

 he differed from him widely in almost every other respect. 

 Van Helmont paid little heed to that part of physiology 

 which is derived by deductions from anatomy, by experiments 

 on animals or by the application of mechanical principles ; 

 Sylvius was well versed in all these things and wrote well 

 on the circulation of the blood and on the mechanics of 

 respiration. Harvey's teaching had apparently no influence 

 on van Helmont; it entered largely into Sylvius's thoughts, 

 and indeed it was chiefly through his advocacy that the 

 Harveian doctrines became established in Holland. Van 

 Helmont's mind was a double one, bent on the one hand 

 on exact careful experiment, turned wistfully on the other 

 hand to mystic speculations about invisible agencies and 

 spirits. Sylvius shared the former mental attitude ; the latter 

 was wholly foreign to his character. Van Helmont was es- 

 sentially an inquirer, most of his time was spent in his own 

 home, pursuing his own researches ; he cared more for fol- 

 lowing out his own ideas than for influencing the opinions 

 of others. Sylvius was essentially an expositor; his own 

 special contributions to the advancement of physiological, 



