BORELLI AND VALISNIERI 



29 



"The true experimental study of digestion is of 

 comparatively recent date ; the ancients were con- 

 tent to find comparisons, more or less happy, with 

 common facts. Thus, for Hippocrates, digestion 

 was a ' coction ' : for Galen, a 'fermentation,' as 

 of wine in a vat. In later times, van Helmont 

 started this comparison again : for him, digestion 

 was a fermentation like that of bread : as the 

 baker, having kneaded the bread, keeps a little of 

 the dough to leaven the next lot kneaded, so, 

 said van Helmont, the intestinal canal never com- 

 pletely empties itself, and the residue that it keeps 

 after each digestion becomes the leaven that shall 

 serve for the next digestion. 



" The first experimental studies on the digestion 

 date from the end of the seventeenth century, when 

 the Academy of Florence was the scene of a 

 famous and long, controversy between Borelli and 

 Valisnieri. The former saw nothing more in 

 digestion than a purely mechanical act, a work of 

 attrition whereby the ingesta were finely divided 

 and as it were pulverised : and in support of this 

 opinion Borelli invoked the facts that he had 

 observed relating to the gizzard of birds. We 

 know that this sac, with its very thick muscular 

 walls, can exercise on its contents pressure enough 

 to break the hardest bodies. Identifying the human 

 stomach with the bird's gizzard, Borelli was led to 

 attribute to the walls of the stomach an enormous 

 force, estimated at more than a thousand pounds ; 

 whose action, he said, was the very essence of 

 digestion. Valisnieri, on the contrary, having had 

 occasion to open the stomach of an ostrich, had found 

 there a fluid which seemed to act on bodies immersed 

 in it ; this fluid, he said, was the active agent of 

 digestion, a kind of aqua fortis that dissolved food. 



