In the earlier part of the 16th century Paracelsus gave a new direction to alchemy by declaring that its true object was not the making of gold but the preparation of medicines, and this union of chemistry with medicine was one characteristic of the iatrochemical school of which he was the precursor.
The history of the alchemical period is treated in more detail in the article Alchemy, and of the iatrochemical in the article Medicine.
This relation of chemistry to medicine prevailed until the 17th century, and what in the history of chemistry is termed the iatrochemical period (see Medicine) was mainly fruitful in increasing the knowledge of compounds; the contributions to chemical theory are of little value, the most important controversies ranging over the nature of the " elements," which were generally akin to those of Aristotle, modified so as to be more in accord with current observations.
From the mazy and incoherent alchemical and iatrochemical doctrines, the former based on false conceptions of matter, the latter on erroneous views of life processes and physiology, a new science arose - the study of the composition of substances.
In the succeeding iatrochemical period, the methods of the alchemists were improved and new ones devised.
The germs of analytical chemistry are to be found in the writings of the pharmacists and chemists of the iatrochemical period.
The founder of the iatrochemical school was Sylvius (1614-1672), who belonged to a French family settled in Holland, and was for fourteen years professor of medicine at Leiden, where he attracted students from all quarters of Europe.