540 APPENDIX. 



mixture, in variable proportions, of these compound cells and 

 of free globules, which, however, it is to be observed, are 

 generally of larger size than those contained within the com- 

 pound or parent cells. Lastly, others of these bodies enclose 

 no compound cells, but are filled with globules of still larger 

 size. (Plate LXIX. fig. 11.) 



" Now the curious part of this history is, that it is these 

 globules which go on increasing in size, and, bursting the 

 envelopes which contain them, ultimately become what are 

 ordinarily regarded as the true fat vesicles. 



" In the article Fat, in an early number of the f Microscopic 

 Anatomy,' I noticed the fact, that the fat vesicles of children 

 are not so large as those of the adult ; this fact it then ap- 

 peared to me had an evident relation to the growth of the 

 fat vesicle, and it suggested the idea that the fat corpuscle 

 was of very slow growth, not attaining its full dimensions 

 until near the adult age ; and that it was permanent in its 

 character, enduring throughout life. This idea gathers in- 

 creased weight, and, indeed its correctness is rendered almost 

 certain, by the additional observations just cited on the deve- 

 lopment and growth of the fat vesicle. 



" It would appear, therefore, taking into consideration all 

 the foregoing particulars, that the principal development of 

 fat vesicles takes place in the advanced foetus, and in the 

 early years of life (for I now remember having met with ' fat 

 cysts' in the great omentum of children of five and six years 

 of age, although at the time of observing them I did not know 

 their nature and meaning), that what are usually regarded as 

 the true fat vesicles or cells, are first contained in parent 

 cells, and lastly, that they are slow in their growth, and per- 

 sistent throughout life. 



" I infer also further, from the foregoing facts, that the 

 ordinary fat vesicles are incapable of acting as parent cells and 

 of reproducing their like ; an inference which might be fairly 

 entertained on other grounds viz., the difficulty, not to 

 say impossibility, of detecting nuclei in them, and the ab- 

 sence of those granules amongst their contents which are so 

 characteristic of true cells, and which there is so much reason 



