410 THE SUPPORTING TISSUES. 



As compared with that of other higher mammals human fat 

 shows no special points of difference in its composition. 



Analysis of Adipose Tissue. The material in question is first 

 dried, ground with a little sand, and extracted successively with 

 ether and alcohol. The alcoholic extract is evaporated to dry- 

 ness, the residue washed with water to remove the soluble salts, and 

 is then extracted with ether. The ethereal extracts are united, and 

 the ether is distilled off, when the fats, lecithins, cholesterins, free fatty 

 acids, and the lipochromes remain. The fatty acids are transformed 

 into their salts by adding a slight excess of sodium carbonate, and 

 heating to a temperature of 100 C. The resulting soaps are ex- 

 tracted with water. The insoluble portion is dissolved in ether, the 

 ether is distilled off, and the residue is heated oh a water-bath with 

 an alcoholic solution of sodium hydrate, which saponifies the fats. 

 The resulting material is extracted with ether, which dissolves the 

 cholesterin. The insoluble residue is dissolved in water, and the 

 solution is saturated with carbon dioxide and extracted with strong 

 alcohol. This takes up the soaps and the glycerin. The alcoholic 

 solution is transformed into an aqueous solution, in which the soaps 

 are decomposed with a dilute acid. The free fatty acids are thus 

 precipitated, and can then be separated from each other according 

 to the usual methods. 



Aside from adipose tissue, fats are met with in all the organs of 

 the body, but, with the exception of the mammary glands during 

 their functional activity, they are found normally only in traces. 

 Under pathological conditions, however, notable quantities of fat 

 may be met with. We then speak of a fatty degeneration of the 

 organs. This is especially observed in the liver in cases of acute 

 yellow atrophy, and can also be brought about artificially by poison- 

 ing with phosphorus, antimony, arsenic, etc. 



Among the fluids of the body, large quantities are normally 

 found only in the milk, and in the chyle during the process of 

 digestion. 



Origin of the Fats. That a portion of the fat that is found 

 in the animal body is directly referable to the fats which have been 

 ingested as such cannot be doubted. This is proved not only by 

 the observation that it is possible to replace the fats which are 

 peculiar to a certain animal by those of another, or even by vegetable 

 fats, as has been shown above, but also by the fact that a gradual 

 deposition of fats occurs in dogs which have been starved an I 

 are then fed on very little albuminous material, but with much fat. 

 In such cases it can easily be proved that the amount of albu- 

 mins ingested is far too small to be the source of the fat that has 

 been stored. 



The ingested fats, however, are not the only source of the fats 

 found in the tissues, and there is evidence to show that they may 

 also be derived from the albumins and the carbohydrates. Their 



