140 THE HISTORY OF BIOLOGY 



it would take too long to enter into fuller details. Van Helmont regards 

 water as the material fundamental element underlying the whole of existence; 

 out of water arises everything on earth, both inanimate and animate sub- 

 stance. As a proof of this theory he cites an experiment: he filled a bowl 

 with loo pounds of dry soil and in it planted a willow, weighing 5 pounds, 

 and watered it with rain-water. After five years the willow-tree weighed 

 164 pounds while the soil, when again dried, weighed about loo pounds 

 less 3 ounces. Thus, he argued, the entire willow-tree was formed of rain- 

 water. This experiment, which indeed was perfectly correct in both plan and 

 execution, although the conclusion he drew from it was wrong, testifies 

 better than anything else that van Helmont was nevertheless a true pioneer 

 in the field of natural science; to have thought out the first biological ex- 

 periment based on quantitative calculations is a service to science which well 

 compensates for many mistakes in the theoretical sphere. Even as a medical 

 practitioner van Helmont showed the same curious mixture of fancifulness 

 and foresight: on the one hand he worked at a mysterious universal medicine 

 which he called "alkahest," while on the other he strongly protested against 

 the abuses common at that time in connexion with violent blood-letting and 

 strangely concocted, excessively strong medicines. Moreover, like Paracelsus, 

 he undoubtedly exercised a strong influence, for both good and evil; his fer- 

 tile, far-seeing ideas proved of value far into the future, and traces of his 

 mystical fancies can even be found in scientists of subsequent generations, a 

 number of whom will be mentioned in the next chapters. 



