62 CONNECTIVE TISSUE. 



is usually largest about the middle iieriod of life, and greatly diminishes in old 

 age. High feeding, repose of mind and body, and much sleep, favour the pro- 

 duction of fat. 'To these causes must be added individual and perhaps hereditary 

 pretlisposition. There is a greater tendency to fatness in females than males ; 

 also, it is said, in eunuchs. Tlie effect of castration in promoting the fattening 

 of domestic animals is well known. 



In infancy and childhood the fat is confined chiefly to the subcutaneous tissue. 

 In after-life it is more equally distributed through the hody, and in i3roportion- 

 ately gi'eater quantity about the viscera. In Hottentot females fat accumulates 

 over the gluteal muscles, fonning a considerable prominence : and. in a less 

 degree, over the deltoid. A tendency to local accumulations of the subcutaneous 

 fat is known to exist also in particular races of quadrupeds. 



Development. — According to Valentin the fat fir.st appears in the 

 human embryo about the fourteenth week of intra-uterine life. It is 

 deposited in the form of minute granules or droplets in certain cells 

 of the connective tissue (fig. 35./,/'): these droplets increase in size 



Fig. 35. — Development of Fat in Cells op Subcutaneous Connective Tissue op 

 NEW-BORN Rat. About 350 diajieters. 



/, /', cells containing fat globules ; in /', the nucleus is visible ; fhr, fibrillated cell ; 

 ■<7, granular corpuscle ; ?, leucocyte ; r, vacuolated cell ; n, n', n", n'", haemapoietic 

 cells ; c, capillary blood-vessel ; c', developing capillary. The fibrils of the tissue are 

 omitted for the sake of clearness. 



and eventually run together so as to form one large drop in each cell. 

 By further deposition this comes to be considerably larger than the 

 original cell, the protoplasm of which remains as a delicate envelope 

 surrounding the fat-drop. By the end of the fifth month the fat-cells 

 have largely increased in number, and have become collected into 

 small groups. Like the other cells of the areolar tissue, the fat-cells in 

 their early state contain a nucleus, but this, as already stated, becomes 

 afterwards hidden from view. 



The deposit of fat within the cells is preceded and accompanied by 

 the formation of a rich network of capillary blood-vessels, which are 

 produced by a transformation of other cells of the tissue in the manner 

 to be afterwards described. 



