356 Transactions of the Society. 



seen it edgeways have as stoutly maintained that it was developed 

 from a branclied or spindle cell. 



Thus it is that Flemming, whose researches, published nine 

 years ago, are prolably the most extensive on this subject, not only 

 insists that fat-cells are developed from the branched fixed cells of 

 the connective tissue alone, but he emphasizes this opinion by 

 declaring that he commenced his investigations in the full belief 

 that fat-cells were developed from wandering cells, and that his 

 investigations forced him to give up this his original idea. Klein 

 also, whose opinions on this question are probably the latest that 

 have appeared in English, does not seem to have worked out the 

 question for himself, but accepts and teaches Flemming's conclu- 

 sions, with the exception of the one where Flemming holds that the 

 fat-cells are developed from the adventitia of blood-vessels. 



He also specially refers his readers to the branched cells of the 

 fossa infraorbitalis of rabbits as the most suitable in which to 

 study the development of fat-cells, and states " that he thinks it 

 unnecessary to warn his readers agamst the possible assumption 

 that the lymph-corpuscles are the elements which become converted 

 into fat-cells." 



Ivanvier, in his ' Traite d'Histologie,' now being published, 

 states distinctly that fat-ceUs are developed from round cells 

 (corps globuleux), and gives drawings which are characteristically 

 clear and trustworthy. He states that he is entirely opposed to 

 Flemming's ideas, and holds that the round cells from which fat-cells 

 are developed are special in their character even from their origin. 

 Of other observers we may briefly note that EoUett holds the 

 opinion that fat-cells are developed from small round granular cells. 

 Virchow and Frey say that in the embryo they are developed from 

 round cells, but they agree with Von Wittich and Foerster that in 

 the intermuscular connective tissue and in pathological formations 

 they are developed from spindle and branched cells. Czajewicz 

 holds that they are developed from small, delicate, flattened cells, 

 which look like spindle-cells when seen edgeways, but he does not 

 even mention the wandering cells, although they were well known 

 when he wrote. Toldt, again, believes that fat-tracts are glandular 

 in their nature ; and lianvier agrees with him so far as to call a fat- 

 cell a unicellular gland. According to Toldt, these glands (fat- 

 tracts) develop from special centres in the embryo, whereas in the 

 adult fat-cells are only developed from pre-existing fat-cells. 



Turning now to our own researches, we wish first to state that 

 we can see no reason lor specially studying the growth of fat-cells 

 in the embryo. They are not embryonic structures in the ordinary 

 sense of the term, but are merely adjuncts to the processes of nutri- 

 tion, whether found in adult or embryo, the process of development 

 being similar in both ; and in studying their life-history under the 



