_Iatrochemists and Iatrophysicists._--During the seventeenth century there was a great deal of disputing among physiologists about the nature of certain processes like assimilation and retrograde metamorphosis, about the manner in which blood is formed, about digestion, and about the rôle played by the lymph vessels. According to Haeser a large proportion of the physicians of that day were confident that chemistry was entirely competent to solve these riddles, and yet, on the other hand, there were not a few who believed that the science of physics, which was then much further advanced than that of chemistry, was quite as competent to explain all the phenomena. At first the split into these two factions was confined to men who were interested in questions of a purely physiological nature, but in a short time the practitioners of medicine were also drawn into the controversy; and from that time onward it became customary to employ the terms, “iatrochemists” and “iatrophysicists” in speaking of the partisans of the two schools of medicine (the iatrochemical and the iatrophysical or iatromechanical). The iatrochemists described digestion as an act that is essentially chemical in character, a form of fermentation; and by the latter term the more advanced members of this school--François Deleboë Sylvius (1614–1672), who was born in Hanau, Prussia, of Dutch parents, and who took his doctor’s degree in Basel in 1637, and Thomas Willis of London (1622–1675)--understood something quite different from our modern conception of fermentation. Their interpretation was as follows: “An internal chemical movement of matter which is set agoing and continued in action in the stomach and intestinal canal through the agency of certain chemical reagents.” (Haeser.) They attributed an important influence to the saliva, the pancreatic juice and the bile in effecting the changes mentioned. The iatrophysicists, on the other hand, and more particularly Archibald Pitcairn of Edinburgh, Scotland (1652–1713), and Giorgio Baglivi of Ragusa, Italy (1668–1707), described digestion as a purely mechanical breaking up of the elements of the food partaken--a “trituration.” As to the further fate of the resulting chyle (its mode of reaching the blood, for example) the two schools were in perfect accord.