154 ON THE ELEMENTARY PARTS OF THE HUMAN FABRIC. 



[Fig- 51. rate, being dissolved in the latter, at the ordinary 



temperature of the body. That the thick oil thus 

 formed does not escape from the fat-cells during 

 life, may be attributed to the moistening of their 

 - 2 walls by the aqueous fluid circulating through the 

 vessels. In all fixed oils, which are fluid at com- 

 mon temperatures, a portion of the solid constitu- 

 ents of fat exists ; these may be separated by ex- 

 Fat vesicles from an emacia. posure to cold, which congeals them, leaving the 

 ted subject; i, i, the cell-mem- Oleine fluid. All these substances are regarded 

 brane; 2,2,2, the solid portion by chemists in the light of salts ; being compounds 

 collected as a star-hke mass, o f ac [^ s t h e Stearic, Margaric, and Oleic with 



with the elaine in connection a common base? to which f rom its swee tish taste, 

 with it, but nor. filling the cell. 1 , r r~ii i 



the name of UJycerme has been given. 



a. Stearine is the essential constituent of nearly all solid fats, and preponderates in propor- 

 tion to their consistence. It exists largely in mutton-suet ; from this it may be obtained by 

 the action of ether, which takes up all the oily matter. It is crystalline, like spermaceti ; 

 it is not at all greasy between the fingers, and melts at about 130. It is insoluble in water, 

 and in cold alcohol and ether; but it dissolves in boiling alcohol or ether, crystallizing as it 

 cools. Stearic acid (the substance of which the slearine candles are composed) may be sepa- 

 rated, by causing it to combine with a stronger base, such as lime or potash, and then setting 

 it free from this by a stronger acid. It crystallizes in milk-white needles; is soluble in its 

 own weight of cold alcohol, and in all proportions at a boiling heat; and fuses at about 158. 

 Its acid powers are sufficient to decompose the alkaline carbonates. Margarine exists in 

 small quantity, along with Stearine, with most fats ; but it is the principal solid constituent 

 of Human fat, which in this respect resembles olive oil rather than the other animal fats. It 

 corresponds with Stearine in many of its properties ; but it is much more soluble in alcohol 

 and ether; and it melts at 116. Margaric acid closely resembles stearic acid in most of its 

 properties; but it is more soluble in cold alcohol; and has a lower melting-point, viz., 140, 

 or thereabouts. It may be procured from stearic acid, by subjecting the latter to a dry dis- 

 tillation. Oleine exists in small quantity in the various solid fats ; but it constitutes the great 

 mass of the liquid fixed oils. The tendency of these to solidification by cold, depends upon 

 the proportion of Stearine or margarine they may contain ; for oleine itself remains fluid 

 at the zero of Fahrenheit's thermometer. It is soluble in cold ether, from which it can only 

 be separated by the evaporation of the latter. Oleic acid much resembles oleine in physical 

 characters, being colourless, lighter than water, and not prone to solidify ; but it has a dis- 

 tinct acid reaction, and a sharp taste, and is miscible with cold alcohol in all proportions. 

 Glycerine, the base of all the fatty acids, may be obtained from any fatty matter, by saponi- 

 fying it with an alkaline base, by which this compound is set free. It cannot be obtained 

 in a solid form, but may be brought to the consistence of a thick syrup. It dissolves in 

 water and alcohol; but is insoluble in ether. It has a sweetish taste, whence its name is 

 derived ; and it is remarkable far its solvent powers, which are scarcely inferior to those of 

 water. The following table shows the atomic composition of the fatty acids, and of their 

 base. 



Stearic Acid .... 68 Carbon, 66 Hydrogen, 5 Oxygen. 



Margaric Acid ... 68 Carbon, 66 Hydrogen, 6 Oxygen. 



Oleic Acid .... 44 Carbon, 39 Hydrogen, 4 Oxygen. 



Glycerine 6 Carbon, 8 Hydrogen, 6 Oxygen. 



The following results of the ultimate analysis of different kind of Fat, show the close 

 correspondence in their composition ; and at the same time make apparent the very large 

 proportion of carbon which they all contain. 



Hog's Lard. Mutton Fat. Human Fat. 



Carbon 79-098 78-996 79-000 



Hydrogen .... 11-146 11-700 11-4 1C. 



Oxygen .... 9-756 9'304 9-584 



100-000 100-000 100-000 



186. Besides the support, combined with facility of movement, which Fat 

 affords to the moving parts of the body, it answers the important purpose of 

 assisting in the retention of the animal temperature, by its non-conducting 

 power; and the still more important object, of serving as a kind f reservoir 

 of combustible matter against the time of need. Herbivorous animals, whose 



