CELLULAR ELEMENTS OF THE GROUND-SUBSTANCE. 25 



out, that these placoids undergo rapid divisions ; one finds, namely, 

 not only cells the nucleus of which is either constricted, or even 

 divided, but the cells themselves show very distinct notches, and 

 more or less deep furrows, by which they become separated into two 

 parts of nearly equal size. 



From these facts we can deduce that by division of these placoids 

 groups of cells result, which lie more or less close to each other, and 

 which possess shorter and fewer processes than those which are to be 

 met with in isolated ones. 



There are, finally, to be found intermediate stages between such 

 vascularised lobules, the cells of which are not transformed into fat 

 cells, and those above-mentioned vascularised true fat lobules. There 

 can be, consequently, no doubt whatever that this hyaline body be- 

 comes transformed into fat tissue in the way that its branched flat 

 placoids become transformed into ordinary fat cells, and that while 

 doing so they proliferate by division, and that these groups are pro- 

 vided with a special system of blood-vessels. The latter may already 

 be found even when the cells of the matrix have not yet transformed 

 into fat cells. 



After having described the development of fat tissue in the gela- 

 tinous body of the infra-orbital fossa, we shall be able to deal with 

 that of the omentum and of the mesentery more briefly than we could 

 otherwise have done, as we find in these membranes exactly the same 

 relations. As regards the formation of fat cells, we find here the 

 same relations. We have had the opportunity to remark that peri- 

 lymphangial vascularised nodules develop from, and consist of, ac- 

 cumulations of more or less flat and branched cells. We had further 

 remarked that these nodules join so as to form whole tracts, which 

 generally follow the course of the larger blood-vessels. We need now 

 only add that if the branched cells which represent the matrix of 

 those tracts become converted into fat cells as above described the 

 result would be what is generally called a vascularised tract of fat 

 cells. That the tracts of fat cells, as well as the more or less isolated 

 fat lobules or fat nodules, are only transformed perilymphangial 

 nodules can be very easily recognised by following a perilym- 

 phangial tract along a large blood-vessel up to a neighbouring fat tract. 



