THE HISTORY OF DIETETICS 423 



lected form in 1897. Eor this work Pavloff received the Nobel prize 

 in 1904. 



The discovery of pancreatic secretin by William Maddock Bayliss 

 and Ernest Henry Starling, announced in 1904, opened up an entirely 

 new field of knowledge, that of the action of the so-called hormones as 

 inciters of secretory activity carried to the points of action by the 

 circulation. 



The introduction of the X-ray made available a new and fertile 

 method of studying the movements of the digestive organs; one of the 

 earliest and most prolific workers in this field has been an American, 

 Walter Bradford Cannon, professor of physiology at Harvard, whose 

 contributions on this subject date from 1899. 



The main basis of dietetics rests in the chemistry of food and 

 nutrition. This knowledge could not be developed until the science of 

 chemistry entered upon its renaissance, which occurred much later than 

 the birth of modern anatomy, physiology and physics. The discovery 

 of oxygen in 1774 opened the way to a rapid development of chemical 

 knowledge, just as Harvey's discovery of the circulation a century and a 

 half before had been the starting point for physiology. 



As has been the case with many other discoveries, the effective dis- 

 covery of oxygen had been anticipated long previously by work that had 

 fallen into oblivion. In 1668 a young Englishman at Oxford, John 

 Mayow (1645-1679), published a remarkable work in which he argued 

 that the atmosphere contains, as he styled it, an " igneo-aereal " or 

 " nitro-aereal " principle which by combining with combustible ("sul- 

 phureous") substances constitutes the process of combustion; that 

 this principle is imparted to the blood by the respiratory activities ; that 

 the union of this principle, carried in the blood, with combustible mate- 

 rial in the muscles gives rise to muscular action and is a source of 

 animal heat. Though this theory was soon forgotten, it was a remark- 

 able presentation of the doctrine of oxidation (including body oxidation 

 as the source of animal energy), and anticipated by a century the 

 discovery of oxygen. 



In 1774 oxygen was independently discovered by Joseph Priestley 

 (1733-1804), an English clergyman, and by Karl Wilhelm Scheele 

 (1742-1786), of Sweden. It was Antoine Laurent Lavoisier (1743- 

 1794), of Paris, however, who grasped the real significance of this dis- 

 covery, and by his researches, published from 1775, overthrew the false 

 though fruitful phlogistic theory of heat that had dominated chemistry 

 for a century, and showed the true nature of combustion and the 

 properties of oxygen. 



Lavoisier was followed by a number of brilliant investigators, who 

 rapidly laid down the great foundations of chemical science. The 

 beginnings of organic chemistry may be traced to some of these early 

 workers; Lavoisier, for instance, showed that organic compounds are 



