DIGESTION. 167 



differences in structure, which are often observable 

 between these two portions of the stomach, would 

 lead to the belief that their functions are in some 

 respects different. 



During digestion the exit of the food from the 

 stomach into the intestine is prevented by the 

 pylorus being closed by the action of its sphincter 

 muscle. It is clear that the food is required to 

 remain for some time in the stomach in order to be 

 perfectly digested ; and this closing of the pylorus 

 appears to be one means employed for attaining 

 this end ; and another is derived from the property 

 which the gastric juice possesses of coagulating, or 

 rendering solid, every animal or vegetable fluid sus- 

 ceptible of undergoing that change. This is the 

 case with fluid albumen : the white of an egg, for 

 instance, which is nearly pure albumen, is very 

 speedily coagulated when taken into the stomach ; 

 the same change occurs in milk, which is imme- 

 diately curdled by the juices that are there secreted ; 

 and these effects take place quite independently of 

 any acid that may be present. The object of this 

 change from fluid to solid appears to be to detain the 

 food for some time in the stomach, and thus to allow 

 of its being thoroughly acted upon by the digestive 

 powers of that organ. Those fluids which pass 

 quickly through the stomach, and thereby escape 

 its chemical action, however much they may be in 

 themselves nutritious, are very imperfectly digested, 

 and consequently aftbrd very little nourishment. 

 This is the case with oils, with jelly, and with all 

 food that is much diluted.* Hunter ascertained 



* A diet consisting of too large a proportion of liquids, although 

 it may contain much nutritive matter, yet if it be incapable of being 



