Histogenesis of the Adipose Tissue. 433 



nary connective tissue cells. In the ox it seems that in general the 

 blood vessels are important factors determining the development of 

 adipose tissue. The connective tissue cells which happen to lie ad- 

 jacent to a blood vessel at the time a fat lobule is forming are the 

 ones which become fat cells. In certain situations, however, as on the 

 kidney and in certain parts of the omentum, so-called primitive organs 

 are developed which bear no close relation to the blood vessels. The 

 blood vessels cannot be regarded as the main determining factors 

 here, though they may take ]3art. 



There is not, however, a random formation of fat cells in the con- 

 nective tissues. The lobules of adipose tissue, in which nearly all 

 new fat cells appear, are well-defined structures. It is only in 



B 





Text Figure 1.3. Two leucocytes trom the omentum of a 16 cm. foetus. 

 II, nucleus ; v, vacuole. Stained with iron-haem. Fixation, Gilson fluid. 

 X 1200. 



the early stages of their formation that cells are added to the lobule 

 from the connective tissue adjacent to the periphery. I intend to 

 treat this phase of the subject more fully in a later paper. 



Text Fig. 13 shows two leucocytes from the omentum of a 16 

 cm. foetus. A great many such cells are present at this stage. They 

 usually contain several vacuoles. By staining with Scarlet red it is 

 seen that these are not fat droplets. It is possible that such cells 

 have lent support to the erroneous conception that leucocytes may 

 form fat cells. 



In conclusion I wish to thank Dr. R. R. Bensley for sending me 

 some necessary material. Most of the drawings accompanying this 

 paper are the work of Mr. G. T. Kline ; a few were made by Miss 

 McGill. 



