236 DIGESTION AND ASSIMILATION OF THE FOODSTUFFS 



depleted of fat-reserves, they are able to exert some measure of control 

 over the nature of the fats which they assimilate. Munk investigated a 

 patient who was afflicted with a fistula from which it was possible to 

 collect the chyle before it entered the blood-stream. When this 

 patient was fed upon a diet containing no other fat than mutton -fat, 

 the chyle-fat had nevertheless a lower melting-point than mutton-fat. 

 When the patient was fed with no fat at all but Cetyl Palmitate, which 

 melts at 55, the chyle-fat was found to melt at 36 and to consist of 

 a mixture of Glyceryl Tripalmitate and glycerides of Oleic Acid to the 

 extent of fourteen per cent, of the mixture, adjudged by the absorption 

 of iodine by the mixed fats. Hence under normal conditions a measure 

 of control is exerted by the intestinal wall itself and a proportion of 

 glycerol and oleic acid may be furnished to supplement the deficiencies 

 of the dietary. This of course becomes impossible if the glycerides of 

 oleic acid which are present in normal tissues have been previously 

 depleted by starvation. 



The fats may also be modified in the opposite direction and the 

 proportion of oleic acid glycerides reduced during their transmission 

 through the intestinal epithelium. Thus when Cod-liver Oil, which 

 contains a great excess of unsaturated fatty acids, is administered to 

 dogs, the iodine number of the fats after absorption is less than that 

 of the fat in the food. 



The absorption of fat leads to a temporary increase in the fat content 

 of the blood, where it is held in a finely emulsified condition. The 

 ingestion of fat-rich foods, as for example, cream, may result in an 

 increase of the fat-content of the blood to no less than six times the 

 normal concentration during the intervals between absorption. Under 

 such circumstances the blood-serum obtained by centrifugalizing 

 defibrinated blood is often cloudy with suspended fat and globules of 

 fat may not infrequently be found floating upon the top of the column 

 of fluid in the centrifuge-tube. Ultimately the excess of fat disappears 

 from the blood, the neutral fats having been built up into the fatty 

 connective tissues. The greater part of the fat-reserve is contained 

 in special fat-cells, in which the fat appears, at first in small globules, 

 and later in larger globules which coalesce until the accumulation of 

 fat forces the protoplasm into the periphery of the cell, so that it 

 presents an annular appearance on cross-section, with the flattened 

 nucleus forming a slight thickening of the ring at one side. Occasion- 

 ally such cells disintegrate bodily, it being in this way that the solid 

 constituents of Milk are formed in the mammary glands. 



Upon allowing fat-rich blood to stand in laboratory-glassware at 

 body-temperatures a proportion of the fat becomes diffusible. The 

 nature of the change which occurs is not yet understood, nor is it certain 

 whether or not this, or a similar change in the properties of circulating 

 fat precedes its absorption by the tissues. Under certain pathological 

 conditions, and particularly in Diabetes, the percentage of fat in the 



