40 



ESSENTIALS OE CHEMICAL PHYSIOLOGY 



a certain percentage of fat, even though all visible adipose tissue is 

 dissected off. The fat-cells are placed between the muscular fibres, 

 and the amount of fat so situated varies in different animals. It is 

 particularly abundant in pork ; hence the indigestibility of this form 

 of flesh : the fat prevents the gastric juice from obtaining ready 

 access to the muscular fibres. 



The follov^ing table gives the chief substances in some of the 

 principal meats used as food. 



The large percentage of water in meat should be particularly 

 noted ; if a man wished to take his daily minimum of 100 grammes- 

 of proteid entirely in the form of meat, it would be necessary for him 

 to consume about 500 grammes {i.e. a little more than 1 lb.) of meat 

 per diem. 



FLOUR 



The best wheat flour is made from the interior of wheat grains, 

 and contains the greater proportion of the starch of the grain and 

 most of the proteid. Whole flour is made from the whole grain 

 minus the husk, and thus contains not only the white interior but 

 also the harder and browner outer portion of the grain. This outer 

 region contains a somewhat larger proportion of the proteids of the 

 grain. Whole flour contains 1 to 2 per cent, more proteid than the 

 best white flour, but it has the disadvantage of being less readily 

 digested. Brown flour contains a certain amount of bran in 

 addition ; it is still less digestible, but is useful as a mild laxative, 

 the insoluble cellulose mechanically irritating the intestinal canal as 

 it passes along. 



The best flour contains very little sugar. The presence of sugar 

 indicates that germination has commenced in the grains. In the 

 manufacture of malt from barley this is purposely allowed to go on. 



When mixed with water, wheat flour forms a sticky adhesive 

 mass called dough. This is due to the formation of gluten, and the 

 forms of grain poor in gluten cannot be made into dough (oats, rice, 



