198 



MANUAL OF HISTOLOGY. 



Fig. 190. a, Human fat-cells com- 

 pletely filled with oil, lying in 

 groups together. 6, free drops ; 

 c, empty envelopes. 



The sustentacular connective-tissue of the nervous centres is reproduced 

 in a number of pathological growths. These have been named " glioma " 

 by Virdwiu. 



8. Fatty Tissue. 



120. 



Fatty tissue, with a specific gravity of 0*924 (W. Krause and L. 

 Fischer), consists of large roundish cells 

 measuring 0'0340-0'1300 mm., and nuclei of 

 0-0076-0*0090 mm., whose thin envelope is 

 usually completely occupied by one single oil 

 globule. These fat-cells usually lie heaped 

 together in considerable groups (fig. 190), and 

 occur in parts formed of connective-tissue of 

 loose texture, the so-called formless species. 

 They generally constitute the complementary 

 substance of the cavities in the latter, which 

 diminishes frequently in quantity between the 

 individual cells of such a group. 



The thin membrane is completely obscured 

 by the dark outlines of the fatty contents, so 

 that cells of this tissue display much similarity 

 to free drops of fat. They show sharply 

 defined dark edges with transmitted light ; but 

 when reflected, their silvery border appears whitish or yellowish white. 

 But, on the other hand, the close crowding to which they are subjected 

 frequently leads to a flattening of adjacent cells at the points of contact, 

 so that they assume a polyhedral form, which does not take place with 



free drops of oil (fig. 190, b), which coa- 

 lesce when pressed one against the other, 

 like those drops of grease seen floating on 

 the surface of soup. 



Careful examination directly of com- 

 pletely filled fat-cells may lead to the 

 conclusion that they possess a membrane, 

 but does not enable us to discover it. 

 For this certain treatment is required. 

 Thus, by increasing pressure, we may cause 

 the very tense membrane to rupture, on 

 which the flaccid empty envelopes of large 

 cells are seen as thin structureless saccules 

 (fig. 190, c). We may likewise extract 

 the contents from the uninjured envelope 

 chemically, by treatment with alcohol and 

 ether. In such cells artificial colouring is 

 necessary before the nuclei can be seen. 



But the fat-cells may deviate more or less from the fundamental form 

 just described. Their contents consist of a mixture of oily and solid 

 neutral fats, always, however, of one which is fluid and soft at the ordinary 

 temperature of the living body. In warm-blooded Vertebrates the 

 cooling of the corpse brings about, not unfrequently, in such as are rich 

 in solid fats, a congelation of the contents. The fat-cells lose, in such a 

 case, their round plump figure and delicate outline, and become rough, 



Fig. 191. Human fat-cells occupied ty 

 crystals, a, Single needles; 6, larger 

 groups; c, cells with groups of the 

 latter in the interior; rf, an ordinary 

 fat-cell without crystals. 



