174: ALIMENTATION. 



ingly soluble in the. oils. Treated with alkalies at a high temperature and in 

 the presence of water, the fats are decomposed into fatty acids and glycerine, 

 the acids uniting with the bases to form soaps. Alkaline, mucilaginous, and 

 some animal fluids particularly the pancreatic juice are capable of holding 

 fat in a state of minute and permanent subdivision and suspension, forming 

 what are known as emulsions. 



The three varieties of fats usually recognized are stearine and palmitine, 

 which are solid at the temperature of the body, and oleine, which is liquid. 

 The formulae for these varieties are the following : 



Stearine (Tristearine), C 57 H 110 6 



Palmitine (Tripalmitine), C 51 H 98 6 



Oleine (Trioleine), C 57 H 104 6 



It is noticeable that in the composition of fats, the hydrogen and oxygen 

 do not exist in the proportions to form water, as they do in the carbohy- 

 drates, and that they are relatively poor in oxygen. One variety of fat can 

 not be converted into another by chemical manipulation. 



As alimentary substances, fats are undoubtedly of great importance. 

 They are supposed by many to be particularly concerned in the production 

 of animal heat. It has been proved by repeated experiments that fat, as a 

 single article of diet, is insufficient for the purposes of nutrition. 



Inorganic Alimentary Substances. It has been shown that all the or- 

 gans, tissues and fluids of the body contain inorganic matter in greater or 

 less abundance. The same is true of vegetable products. All the organic 

 nitrogenized matters contain mineral substances which can not be separated 

 without incineration. When new organic matter is appropriated by the tis- 

 sues to supply the place of that which has become effete, the mineral sub- 

 stances are deposited with them ; and the organic matters, as they are trans- 

 formed into excrementitious substances and discharged from the body, are 

 always thrown off in connection with the mineral substances which enter into 

 their composition. This constant discharge of inorganic matters, forming, 

 as they do, an essential part of the organism, necessitates their introduction 

 with the food, in order to maintain the normal constitution of the parts. 

 As these matters are necessary to the proper constitution of the body, they 

 must be regarded as alimentary substances. 



Water. This is one of the most important of the constituents of the 

 organism, is found in every tissue and part without exception, is introduced 

 with all kinds of food and is the basis of almost all drinks. As a rule it is 

 taken in greater or less quantity in a nearly pure state. Although, as a 

 drink, water should be colorless, odorless and tasteless, it always contains more 

 or less saline and other matters in solution, with a certain quantity of air. 

 The air and gases may be driven off by boiling or by removing the atmos- 

 pheric pressure. The demand on the part of the system for water is regu- 

 lated, to a certain extent, by the quantity discharged from the organism, and 

 this is subject to great variations. The quantity taken as drink also depends 

 very much on the constitution of the food as regards the water which enters 

 into its composition. 



