Occurrence of Fat. 407 



and the mcdnllarj renal tubules. ]^o fat was found in the psoas 

 muscles. 



51 cm. fcetus. The liver contains a large amount of fat. Some 

 of the droplets seem to be in the endothelial cells, but this point could 

 not be determined satisfactorily. No fat was found in the fibers of 

 psoas muscles. 



85 cm. foetus. The liver contains many tine fat droplets. Most 

 of the droplets seem to be between the hepatic cells as in the 51 cm. 

 specimen. 



105 cm. foetus. The muscle fibers of the psoas muscle contain 

 no fat, but fat cells are present around a few large blood vessels 

 in the coarse intermuscular septa. 



The above observations, though not as complete as might be desired, 

 show clearly that fat occurs in the protoplasm of many of the foetal 

 tissues both before and after the formation of true adipose tissue. 

 It is present in some tissues at least before any preadipose tissue 

 has been formed. It may be present in the liver at any foetal stage. 

 The greatest fluctuations in quantity are found in the liver. Some 

 of the observed variations in the quantity of fat present are surely 

 due to variations in the distribution of fat in the organ. One cannot 

 examine every part of a large organ, and it is very improbable 

 that the fat is always uniformly distributed. 



The fat seems to disappear from the muscle fibers about the time 

 of the first formation of true adipose tissue. But, notwithstanding 

 this apparent connection, it seems to me that the fat in the muscle 

 fibers is not merely stored fat. As pointed out in the 7 cm. foetus 

 described al)Ove, the presence of the fat seems to be intimately con- 

 nected Avith the growth of the muscle fibers. It is probal)ly required 

 in the metabolism of the fiber in the early stages of its develop- 

 ment. 



The occurrence of fat in the tissues of cattle nine months or more old. 



Fifteen animals have been slaughtered thus far in our experi- 

 ment. In these the liver, kidneys, salivary glands, pancreas, and 

 thymus have been carefully examined for the presence of fat. For- 



