THE METABOLISM OF FAT 



285 



Albert finds that the fat in swine and sheep is subject to very 

 considerable individual variations as to melt-point, refractive index, 

 and iodine number. The difference depends on the food and 

 external temperature. Even in the- same individual the fat is not 

 of the same composition in different parts of the body, but varies 

 in the superficial parts exposed to cold. 



The following figures show the effect of exposure to cold 

 (Henriquez and Hansen) : 



The paniculus of the new-born infant is a harder fat than that 

 of the adult, owing probably to the sheltering warmth of the uterus. 



In the fat of an Esquimaux girl, aged twelve, fed on fish, 

 Rosenfeld found an iodine number of 79, while that of a European 

 of the same age is 61. 



The metabolism of fat can be investigated either by the 

 Pettenkofer or Zuntz method. Atwater in America has perfected 

 a most complete calorimeter and respiration chamber, in which a 

 man can live many days working if required on a bicycle which 

 drives a friction wheel, sleeping on a proper bed, and receiving 

 his victuals and handing out his urine and faeces for analysis 

 through a double window. A steady current of air ventilates the 

 chamber, and by analysis of the incoming and outgoing air the 

 respiratory exchange is arrived at. The heat given off is measured 

 by circulating through the double walls of the chamber a constant 

 stream of water which has previously been cooled to a constant 



