402 PHIJ.OSOPHICAL TRANSACTIONS. [ANNOldg^, 



a difi'ereiU nature, is no sooner inclosed in the stomach, and digested in the 

 heat of that and the adjacent parts, but the more spirituous and subtile parti- 

 cles are put into motion, both from that warmth and the difference of their 

 natures, and commence a fermentation; and so by their intestine commotion, 

 and the violence they offer to those parts which oppose the tendency of any of 

 them, they break and dissolve the more solid parts. Again: some suppose that 

 this ferment is supplied from the glands of the stomach. And lastly, others, 

 and perhaps with much better reason, contend for the saliva, and make that to 

 be the ferment wliich serves principally for the digestion of the food ; which in 

 mastication being mixed with our aliment, is with that carried down into the 

 stomach, where its parts being put into motion by a kindly and agreeable heat, 

 they ferment with and agitate first those parts of the food which are most 

 apt to ferment with it, and then both conspire to break and dissolve the grosser 

 and more stubborn parts. And Galen plainly allows that the saliva is concern- 

 ed ill the business of concoction; though he supposes the alteration, which is 

 produced by this juice, to be made in the mouth. 



Having given this short account of the various opinions of some Ingenious 

 men, concerning the manner how concoction is performed; I come now to pro- 

 pose my own hypothesis, by which I shall endeavour to explain it. 



In order to the more easy and effectual digestion of the food, nature has ap- 

 pointed some parts for breaking our aliment, and reducing whatever is gross 

 into smaller parts, before it is put upon digestion : others to supply the ferment, 

 by which it is to be dissolved and concocted, aud which, before it comes to be 

 included in the stomach, moistens and makes it softer, that it may more easily 

 be penetrated and broken by those parts which serve to divide every morsel into 

 smaller pieces. 



For breaking that part of our food which is not liquid, nature has furnished 

 us with teeth, and those of two sorts ; some are appointed to divide and break 

 off smaller morsels from a larger mass ; others for grinding those morsels into 

 much smaller parts. The teeth which serve to break off" pieces of a convenient 

 magnitude from a larger mass are of two sorts, accommodated to the nature of 

 the substance which we eat : these are the incisores, and the dentes canini. If 

 the substance which we have to eat be not hard, but more easily penetrated 

 and divided, then the incisores are capable of making an impression upon it, 

 and fixed firmly enough in the jaws to break off that part which they take hold 

 of. But if it be more solid, and not easily penetrated, nor any piece without 

 difficulty to be separated from that body of which it is a part, then we apply 

 the dtintes canini or eye-teeth to it, which are not spread, nor have such an 

 ed"-e as the incisores, but are sharp and pointed like an awl, and so do more 



