380 FAT METABOLISM. OBESITY 



amount of fat injected under the skin presents, of course, a 

 relatively small surface for attack by such ferments, and for 

 this reason it seems possible to very materially improve the 

 resorption by introducing the fat in the form of affixed emul- 

 sion. In spite of the fact that in occasional experiments it 

 has seemed possible to distinctly prolong the life of starving 

 animals by subcutaneous injections of fat, the hopes which 

 were entertained by clinicians of being able to feed by sub- 

 cutaneous injection of fat, because fat contains in the 

 smallest volume the largest amount of energy (measured in 

 calories), have for the present at least entirely failed of 

 realization 23 (v. infra, Chapter XX). 



FatStorageinttieBody. The amount of fat stored in the 

 economy is very considerable even under normal conditions. 

 In a healthy human being it has been estimated at about 18 

 per cent, of the body-weight. The importance of the energy 

 thus accumulated can be readily appreciated when one thinks 

 of the long periods of fasting and the diseases which can be 

 endured in which the intake of food seems to be reduced to a 

 minimum. A study made in Pfliiger's laboratory 3 showed 

 in a well nourished dog a fat content equivalent to more than 

 one-fourth of its body weight ; about one-half of the fat was 

 obtained from the skin and subcutaneous tissue, and one- 

 third from the musculature, so that only a comparatively 

 small proportion was distributed in the other tissues. In a 

 fattened animal as much as a third or even a half of the live 

 weight may be represented by fat. The large quantities of 

 glycogen which the liver ordinarily contains during full car- 

 bohydrate diet, are supplanted by fat in case of forced 

 feeding with the latter, thus bringing out the antagonism 



2 aW. v. Leube, 1895; E. Roll, 1898; Hofbauer, 1903; H. Winternitz, 1903 

 and 1906. Literature : A. Magnus-Levy and L. F. Meyer, Handb. d. Biochem., 4', 

 448-449, 1909; and E. Heilner (Munich), Zeitschr. f. Biol., 54, 54, 1910. 

 J. Henderson and E. F. Crofutt (Yale Med. School) , Amer. Jour, of Physiol., 1%, 

 193, 1905. 



8 K. Mockel, Pfliiger's Arch., 108, 189, 1905. 



