405 PHILOSOPHICAL TRANSACTIONS. [aNNO IGQQ. 



collision, which strikes off smaller particles from the larger parts ; sometimes 

 by a compression, when the particles which are in motion happen to strike 

 directly against any grosser part on every side of it ; and sometimes by a kind 

 of explosion. For without doubt the saliva, which is fluid, insinuates into the 

 interstices of the grosser parts of the aliment ; and whatever is agitated and ex- 

 panded in those interstices, requiring a larger space for the freedom of its mo- 

 tion, and offering a violence to every thing that opposes its tendency, will, like 

 gunpowder included in a shell, force its way out, and tear to pieces the matter 

 which endeavours to confine it. 



Thus the grosser parts are broken and divided, until they are at least so far 

 attenuated, as to mix more equally with the fluid, and with them to make one 

 pulp or chylous mass. And although I do not apprehend how the stomach 

 should by its reciprocal motion in inspiration and expiration be able to break 

 and attenuate any matter that will not be softened and dissolved by agitation \u 

 a liquid, yet it is certain that these motions, caused by the diaphragm and ab- 

 dominal muscles in respiration, make those parts which are broken ofi^", as they 

 are dissolved, mix intimately with the liquid, as the meat which I digested with 

 oil of turpentine and oil of vitriol did by agitation mix more equally with the 

 oils, and became a pulp. 



As the juices which constitute the saliva ferment on their mixture, so it is 

 probable that from their mixture and fermentation there results such a tertium 

 quid, as is apt to ferment with the bile. And therefore, when the aliment has 

 been a sufiicient time under the fermentation excited by the saliva, it is then 

 thrown into the duodenum, where it meets with the bilious juice, which flows 

 into that intestine from the liver, from which a new fermentation seems to 

 arise ; and the commotion of the parts of the aliment being still continued, 

 carries on the business of digestion, till the food is perfectly concocted. 

 Though it is probable, that this new fermentation serves not only for the more 

 perfect digestion of the food, but likewise for the separation of the chyle from 

 the feculent parts. Neither do I by an ungrounded conjecture suppose that 

 from the mixture and fermentation of the two juices, which constitute the 

 saliva, there^ results a matter which is apt to ferment with the bile; but the 

 notion was confirmed by an experiment : for considering that the bile is generally 

 allowed to have much of a saponaceous nature, I made a solution of soap in fair 

 water, and mixed it with the oils of turpentine and vitriol first put together, 

 and from their mixture I observed a gentle fermentation, which continued for a 

 considerable time. * 



* This doctrine of digestion being performed by fermentation is now exploded. See vol. iii. p. 7 1, 

 of ihis Abridgment, 



