88 PRACTICAL HISTOLOGY. 



ment of the method of interstitial injection with 

 gelatine (see Preparation 6, p. 76). The gelatine is 

 injected into the interior of one of the fat-lumps, 

 and sections are made and treated in the way as 

 described. By this method the fat-cells are some- 

 what separated from one another, and all their parts, 

 as well as the intermediate tissue and bloodvessels, 

 are much better displayed. 



Preparation 18. Membrane of the fat-cell. 

 To show this distinctly Ranvier's method may be 

 recommended. An interstitial injection is made 

 with a weak solution of nitrate of silver (1 in 1000), 

 with a minute portion of the fat-lump thus rendered 

 cedematous is removed with scissors, transferred to 

 a slide and covered. Many of the fat cells exhibit 

 the envelope and nucleus separated by a distinct 

 space from the fat-drop. The silver solution would 

 appear to have penetrated by endosmosis and to have 

 become collected between the fat-drop and its inclos- 

 ing membrane. 



Preparation 19. To complete the study of adi- 

 pose tissue, the fat-cells should be observed in pro- 

 cess of development. For this purpose a preparation 

 of the subcutaneous tissue from a part where fat is 

 being deposited may be obtained from the moderately 

 advanced foetus of any mammal. The new-born rat 

 is especially to be recommended, since in its subcu- 

 taneous tissue there are generally to be found, not 

 only cells which are in every stage of fat-deposition, 

 but others in addition which exhibit the formation 

 of bloodvessels and the simultaneous formation with- 

 in the same cells of red-blood corpuscles. The mode 

 of preparation is very simple, all that is necessary 

 being to strip the skin from the back, snip oft' with 

 scissors a little of the gelatinous-looking tissue from 

 the borders of a tract where the fat is already partly 

 deposited, and to place the portion so obtained in a 

 drop of salt solution upon a slide, and cover it with 

 a thin glass. 



