166 Sylvius and Ms Pupils. [lect. 



" that they can hardly be broken by the molar teeth of man, I 

 " introduced some of these by the mouth into the stomachs of 

 *' turkeys and observed on the following day that they were 

 "broken and pulverized. And because it might be supposed 

 " that their woody husks had been macerated and softened by 

 "some fermentative juice, I forthwith introduced into the 

 " stomachs of other turkeys glass vesicles, so stout that they 

 " could with difficulty be crushed with the teeth, and I found 

 " these on the following day in the faeces reduced to powder. 



" Hence since the action of these two organs, that is to say, 

 "the teeth and the fleshy stomach is similar, for they act by 

 " pressure like a winepress, and overcome the same resistance, 

 "viz. the hardness of the same glass vesicles, we may therefore 

 " conclude that the motive powers of the two are equal. But 

 " we have already shewn that the absolute force of the muscles 

 "which close the human jaw represents a power greater than 

 "that of a weight of 1350 lbs. Therefore the force of the 

 " turkey's stomach is not less than the power of 1350 lbs." 



Borelli, as we have just seen, though he appears to think 

 that in most birds the digestive action is wholly mechanical, 

 and indeed he maintained that the pebbles in the stomach 

 might be not only mere mechanical aids, but when crushed 

 might serve for nutriment, admits in the case of some stomachs 

 a corrosive juice. In this point as in others the followers of 

 Borelli went beyond their master, and the iatro-physical school 

 after him were prepared to deny chemical action in all cases, 

 and to maintain that digestion was in reality a mere trituration 

 of the food by the muscular mill of the stomach into the creamy 

 mass known as chyle. 



The iatro-chemical school on the one hand, following van 

 Helmont and Sylvius, contended that the change in the stomach 

 was chiefly if not wholly a chemical change effected by a 

 process of fermentation. Opinions differed however as to what 

 was the efficient agent of the process. It was generally recog- 

 nized that the lining membrane of the stomach was glandular 

 in nature ; this in many creatures, such as birds, was obvious. 

 But many were inclined to attach greater importance to a juice, 

 such as the saliva, which was poured forth by a conspicuous 



