FATS LECITHIN CHOLESTEROL. 109 



of fats. The former found that a dog, weighing 35 kilograms, assimilated 

 98 per cent of 350 grams of fat administered in a day. Rubner main- 

 tains that the intestine of a human being can absorb a like quantity. As 

 a rule, however, 100-120 grams is about as much as the system can 

 stand. 



The blood also shows changes after the absorption of fat. Chyle, charged 

 with fat, is continually poured into the blood-stream through the thoracic 

 duct. The blood, and especially its plasma, quickly shows an increased 

 fat-content. This is especially true if the fat absorbed is large in amount, 

 and is indicated by a milky turbidity, of an otherwise clear plasma. 

 Often a distinct separation of drops of fat on the surface can be obtained 

 by placing such plasma in the centrifugal. Ultimately the excess of fat 

 again disappears from the blood. The process by which this is accom- 

 plished has not yet been demonstrated. The globules of fat do not 

 migrate through the capillary walls. It is possible that the leucocytes 

 have some function here. At one time it was considered certain that the 

 blood contained a lipase. Why it should be present, however, was not 

 clear, because, through the syntheses in the intestine, the organism protects 

 itself against free fatty acids. Why, then, should the fat be decomposed 

 again in the blood? This hypothesis has been abandoned, but on the other 

 hand the investigations of Connstein and Michaelis * have shown that blood 

 possesses the ability to transform fats into unknown substances, which 

 are soluble in water and capable of dialysis. This process is dependent 

 upon the presence of oxygen, and seems to require the interaction of the 

 red corpuscles. A part of the absorbed fat is taken directly to the tissue- 

 cells and consumed. 



The unused fat is stored away as such. This is evident from the 

 following experiments. Franz Hofmann 2 allowed a dog to fast until it 

 was devoid of fat. The beginning of this period can be ascertained by 

 estimating the amount of excreted nitrogen. The starving animal utilizes 

 its stores of glycogen and then of fat, keeping its albumin intact as long 

 as possible. If the fat supply is used up, a rapid decomposition of albumin 

 takes place. The nitrogen elimination increases immediately. This occurs 

 in from four to six weeks. Hofmann then fed the animal under inspection 

 with considerable bacon and little meat. The amounts of fat and albumin 

 given were accurately determined. It was found that in five days this 

 dog assimilated 1854 grams fat, and 254 grams albumin; and stored up 

 1353 grams fat. This proved that fat in food is utilized to increase the 

 fat supply in the body. Pettenkofer and Voit 3 reached the same conclu- 



1 Sitzungsber. Akad. Wissensch. zu Berlin, 771, 1896; Pfluger's Arch. 65, 473 

 (1897) ; 69, 76 (1897). Cf. Ergebnisse d. Physiologie, 3, 1, 194. 



2 F. Hofmann: Z. Biol. 8, 153 (1872). 



3 Loc. cit. Z. Biol. 9, 1 (1873). 



