FAT METABOLISM 727 



anhydrid and H 2 SO 4 (con.) until the bluish color is fully developed (Liebermann reac- 

 tion), the intensity of which is then compared in a colorimeter with that obtained by 

 similar treatment from a standard cholesterol solution. 



Variations in Blood Fat. In the dog the percentage of fat in the 

 blood is remarkably constant under normal conditions. After a fatty 

 meal the increase in fat begins in about an hour, and reaches its maxi- 

 mum in about six. The increase is not found in animals in which the 

 thoracic duct has been ligated. Although this result would seem to 

 support the view that fat absorption occurs exclusively into the tho- 

 racic duct (page 723) it must be remembered that the evidence is not 

 convincing since the shock caused by so severe an operation may account 

 for the faulty fat absorption. 



Very interesting results have been obtained following the intravenous 

 injection of emulsions of oil, either the so-called casein emulsion or col- 

 loidal suspensions. Up to a dose of 0.4 gram per kilogram of body 

 weight which by calculation would suffice to raise the fat content of 

 the blood by 100 per cent there was no increase in fat content. In or- 

 der to explain this disappearance of fat, it might be imagined that the 

 injected fat particles formed emboli in the smaller capillaries. Against 

 such a view, however, is the fact that the particles of fat in these emul- 

 sions are one-half to one-seventh the size of a red corpuscle. Although 

 this argument is no doubt of some weight, it should be remembered 

 that the physical condition of these fine fat globules is not the same as 

 that of the red blood corpuscle. Their surface condition may be such 

 that they readily agglutinate so as to form small masses, which may 

 stick at the branching of the smaller arterioles and capillaries. Bloor 

 himself suggests that the injected fat may be stored, possibly in the liver, 

 since the fat in this organ, as we shall see later, increases under similar 

 conditions. When twice the above quantity was fed in the form of egg- 

 yolk fat, some of it persisted in the blood for several hours. This in- 

 crease may have been owing to the flooding of the temporary storehouses 

 with fat, or, more probably, to a retarding influence that lecithin may 

 have on fat assimilation, for lecithin itself persists in the blood for a 

 long time after intravenous injection. 



During fasting, no increase in blood fat was found unless the animal, 

 by special feeding, had been stuffed with excess of fat prior to the fast- 

 ing period. The lipemia in this case indicates that fat is being trans- 

 ited from one place to another to serve as fuel for the starving tissues. 

 Narcotics were found to produce an increase in blood fat. Ether pro- 

 duced this increase during the narcosis, whereas morphine and chloro- 

 form did not do so until after recovery. The explanation given for the 



