TISSUES OF THE BODY. 



203 



195. Tissue of the gelatin of Wharton, serving at 

 the same time to explain the development of form- 

 less connective -tissue, a, connective -tissue cor- 

 puscles; 6, fasciculi of connective-tissue; c, spheri- 

 cal formative cells, possibly passing into fat-cells. 



124. 



The development of fat-cells in the embryo, and the nature of the 

 tissue at an early age, is partially understood. The former takes place 

 along the course of the blood- 

 vessels (early or late according 

 to the locality) (Flemming, 

 Toldt), possibly by the meta- 

 morphosis of roundish cells 

 bearing more of an embryonic 

 character (Virchow, Frey, Rol- 

 lett), or from connective-tissue 

 cells (F lemming}. There is 

 no doubt, however, that later 

 in life a formation of fat-cells 

 does take place frequently in 

 connective-tissue by metamor- 

 phosis of its cells. 



Reserving the consideration 

 of its development in the hol- 

 lows of rudimentary bone, we 

 will here discuss the formation 

 of fat-cells in formless connec- 

 tive-tissue. 



This takes place possibly 

 from the spheroidal cells which occupy the interstices of rudimentary 

 formless connective-tissue (fig. 195, c, c). By the segmentation of 

 the former, groups spring up, which fill up these spaces at a later 

 period. 



According to Valentin's statements, which, however, neither Gerlach nor 

 myself have been able to verify, there 

 may be seen isolated adipose cells, 

 but still destitute of fat, in the sole 

 of the foot and palm of the hand of 

 very young human embryos e.g., of 

 fourteen weeks old. 



At a later period (fig. 196, 2), the 

 fatty tissue presents very peculiar 

 appearances. Spheroidal cells (a, b) 

 of considerable size, containing vesi- 

 cular nuclei, and finely granular 

 contents, lie crowded together in 

 the usual characteristic manner (c), 

 squeezed into polyhedra, and en- 

 closed in the well-known vascular 

 network. As yet, however, they 

 contain no oil globules. The cells 

 of a 10-inch sheep's embryo are 

 about half as large as those in 

 the full-grown animal, while the 

 nuclei are on an average 0'0066 

 mm. Now commences (apparently) the very interesting and gradual pro- 

 cess by which the cell is filled with fatty matters, which may be ob- 



Elg. 196. 



