Development, &g., of the Fat-cell. By O. and F. E, Eoggan. 359 



now ready for examination, or for being mounted permanently as 

 a preparation. 



Although this process of staining is by far the quickest and best 

 for showing the development of fat in cells, it will be found advisable, 

 more especially when studying their disappearance, to reverse the 

 method, and, after treatment with silver solution, to treat the mem- 

 brane first with osmic acid, to render the fat quite black, and then 

 with logwood solution, to render the cells and their nuclei evident. 

 But whatever processes the membrane may be subjected to, it will 

 always be advisable to examine it from time to time under the 

 Microscope, the membranous surface of the tambourine being 

 placed uppermost on the stage ; and, as may easily be conceived, it 

 may thus be continually subjected to examination without touching 

 anything or its receiving any injury whatever. 



Instead of commencing with the ancestry of the fat-cell, we find 

 it more convenient to start from the first appearance of fat-globules 

 within one, and to trace their gradual increase until we reach 

 the fully charged fat-cell. This condition is well shown in Fig. ], 

 from the broad ligament of the uterus in a well-nourished pregnant 

 mouse. At a we see the first sign of fat making its appearance, as 

 two minute oil-globules within a cell, one on each side of the cell- 

 nucleus. At h we have a stage further advanced, and notice three 

 fiat-globules within a cell, each of the globules being larger than 

 either of the two globules seen in the cell last described. In this way 

 we may trace the progressive development of fat in c, d, e, and /, 

 where the large fat-globules which fill the cells are on the point of 

 running together to form the fully developed fat-cells seen in Figs. 4 

 and 6. Let us now return to cell a, and proceed in the opposite 

 direction. All the cells we have referred to lie between the layers 

 of endothelium covering both surfaces of the membrane, or, in other 

 words, in the substance of the membrane itself. Now, there can be 

 no doubt that cell a is of the same nature as cell g, in which no fat- 

 globules have as yet appeared, and which lies like the rest in the 

 substance of the membrane. But g is evidently similar to cell h, 

 which is certainly a wandering cell lying external to the membrane, 

 for it has placed itself in one of the natural holes which are so 

 plentifully found in such membranes ; it is evidently similar to 

 the group of wandering cells seen near cell e, all of which, by the 

 binocular Microscope, may be seen to lie on the free surface of the 

 endothelium, over which they were travelling when the silver solu- 

 tion killed and fixed them in that position. Other minor features 

 stamp these as being wandering cells ; thus cell i possesses two 

 nuclei, h has a purse-shaped nucleus where the one is about to 

 become two, while aty we have the early stage or type of the newly 

 born wandering cell ; so that even without going further we might 

 venture to conclude that fat-cells are developed from wandering cells 



