FATS LECITHIN CHOLESTEROL. 1 1 1 



On the contrary, on leaving the blood-stream in a diffusible condition, at 

 present not understood, it is taken up by certain cells, and there converted 

 into fat. The fat-cells themselves are supplied with an efficient resisting 

 membrane. It withstands the action of alcohol and ether, and is not 

 dissolved by acetic and dilute mineral acids. The fat-cells also contain a 

 yellow color principle. Like all cells they contain protoplasm, for which, . 

 however, there is only a limited space if the fat supply be large. The 

 fatty tissue is closely interwoven with that of the network of blood- 

 vessels, so that this valuable material may be quickly utilized when 

 necessary. We do not know how this reserve material is liquefied. It 

 has not yet been determined in what form the fat leaves the cell and enters 

 the blood-stream. Nervous influences undoubtedly control these large fat 

 supplies, so that the fat cells are in this way kept in unbroken relations 

 with the general metabolism. It is not improbable that the fat-containing 

 cells of the connective tissue (i.e., the protoplasm which they contain) play 

 in the metabolism of the fats, a role similar to that taken by the cells of 

 the liver in carbohydrate metabolism. As the latter build up glycogen 

 from grape-sugar and so protect the excess of carbohydrate from oxidation, 

 and in case of need either directly or indirectly bring about cleavage, so the 

 fat-cells withdraw from the blood the excess of valuable fat material, 

 retaining it for a time, in order to set it free again for oxidation at the 

 required moment. The animal organism has an efficient supply of reserve- 

 material in the fat. It possesses double the calorific value of carbohy- 

 drates and of proteins. One gram of albumin gives 4. 1 calories, one gram 

 carbohydrate gives likewise 4 . 1 calories, while one gram fat, on the other 

 hand, gives 9 . 3 calories. In fasting, the fat supply is very quickly drawn 

 upon. Ordinarily the normal organism keeps this supply very constant. 

 Gradually, equilibrium is established to a certain extent between the 

 amount of the food which is used as fuel and that used for the replace- 

 ment of tissue. This, of course, applies only to the mature organism. 

 In man, frequently, this equilibrium is disturbed. More fat is in many 

 cases being added constantly, so that the fat deposits grow far beyond the 

 physiological requirements, and finally a condition results which is vari- 

 ously known under the names of adiposity, obesity, and polysarchia. It 

 is impossible to distinguish sharply between such fleshiness and a physi- 

 ological reserve supply of fat. Only when difficult breathing and faulty 

 heart-action are indicated, does the condition become a pathological one. 

 The causes of obesity are unknown. Various conditions can lead to this 

 same result. There is unquestionably a physiological obesity, which arises 

 from a rich diet, and a pathological obesity, which occurs in spite of all 

 precautions. The latter form belongs to the class of metabolic derange- 

 ments, and can be traced to an abnormal metabolism of the cells. It is 

 certain, that, until we are better acquainted with the subject of physiological 



