CHEMISTRY AND ITS DEVELOPMENT 207 



May erne (1573-1655), Andreas Libavius (M616), Oswald 

 Croll, Adrian van Mynsicht, and the great Van Helmont 

 (1577-1644). Van Helmont not only realized that the 

 processes of life, in health and disease, are largely depend- 

 ent upon chemical changes, but he abandoned the abitrary 

 assumptions of Paracelsus concerning the chemical basis 

 of the animal body, and his keen experimental researches 

 imparted a powerful impulse to the development of scien- 

 tific medicine. Equally if not more important was his recog- 

 nition of the fact that there may be other gases than air, 

 and that atmospheric air, ' ' carbonic acid, ' ' hydrogen, marsh 

 gas and ''sulphurous acid" may be quite different from 

 one another. In certain special cases Van Helmont suc- 

 ceeded in showing that substances are not lost, either qual- 

 itatively or quantitatively, when they enter into chemical 

 combination, and that they may be re-obtained from the 

 resulting compounds. Yet he believed in the possibility of 

 making gold, and, strange to relate, among the absurdities 

 found in his writings is the assertion that mice may be 

 spontaneously produced in buckets filled with soiled linen 

 and wheat flour ! But if the spirit of the time permitted 

 such beliefs, so much more deserved is his place among the 

 best names of both chemistry and medicine. Other im- 

 portant names connected with iatrochemistry are those of 

 Silvius (1614-1672) and Tachenius. Silvius was the first 

 to grasp the similarity between the processes of respiration 

 and combustion, and, recognizing the distinction between 

 arterial and venous blood, he understood that the bright 

 color of the former was due to the action of the air. Di- 

 gestion, too, he considered as a purely chemical process. 

 His pupil, Tachenius, was the first to clearly recognize that 

 salts are substances formed by the union of acids and 

 bases; he studied the composition and properties of many 

 substances, invented a number of interesting qualitative 

 tests, and even subjected a few reactions to quantitative 

 investigation ; determining, for instance, the gain in weight 

 involved in the oxidation of lead. 



