Development, &c., of the Fat-cell. ByG. and F. E. Hoggan. 367 



the trap been set above ten hours previously, showing how rapidly- 

 fat may become formed' within previously exhaasted fat-cells in 

 these little animals. 



It may also be well to state here that the normal shape of a 

 fat-cell, when it is not distorted by the pressure of contiguous 

 structures or fat-cells, is generally oval and sometimes round, as 

 shown in Figs. 4 and 6, the irregularly polyhedral shape drawn and 

 insisted upon by Kanvier being due entirely to distortion by pres- 

 siu'e of contiguous cells, and therefore in no way representing the 

 normal shape. The influence of pressure in distorting fat-cells may 

 easily be traced in Fig. 6, where cells a, a, a, at the border of a 

 fat-tract lying along the blood-vessels in the mesentery of a guinea- 

 pig, have their free borders rounded oif, while on the sides pressed 

 upon by contiguous fat-cells h, h, they are becoming angular and 

 irregularly polyhedral in shape, of the form indeed in which they are 

 generally represented. 



Hitherto there has been no question of a cell- wall or membrane, 

 for all histologists agree that the wandering cell does not possess 

 one, and indeed it is generally presented as the type (often under 

 some other of its names) of a wall-less cell, whereas the fat-cell is 

 almost invariably presented as the type of an animal cell possessing 

 a true wall or membrane, and it therefore becomes of importance to 

 inquire how far we are justified in accepting it as such a type. 

 Eanvier and others, in tracing the development of the fat-cell from a 

 wall-less cell, go so far as to localize the time when the v/all is formed, 

 and state that it is only when the fat-globules have pushed the 

 nucleus from the centre of the cell to its periphery that the cell- wall 

 begins to be formed. 



Now, with all due deference to the opinions of other observers, 

 we feel called upon to state that, even after careful searching and 

 studying the fat-cell in all its phases, we find no evidence whatever 

 of the existence of a special cell-wall, that is to say, in the sense in 

 which the term is generally understood. We cannot admit that 

 there is any change whatever in the nature of the cell-substance or 

 protoplasm, although in fully developed fat-cells like those in 

 Fig. 6 it has become so distended and attenuated by the mass of 

 fat growing within it, that it appears to surround the latter like a 

 thin sheet. Still that thin sheet is only unaltered protoplasm, and 

 we shall afterwards see that, when absorption of the fat from the 

 fat-cell occurs, the so-called membrane contracts upon the lessening 

 fat, becoming thicker as the fatty contents become smaller in a way 

 a formed membrane would not do, and when the fiat wholly disap- 

 pears, the cell-substance remains behind in the same protoplasmic 

 condition in which it existed in the parent-cell. If any observer 

 has observed before us the behaviour of the cell-protoplasm during 

 absorption of fat, we cannot understand how he could reconcile 



