364 Transactions of the Society. 



that the fixed cell of the connective tissue is a broad flat cell, 

 " cellule plate" which, when applied to fibres, has the appearance, 

 but only the appearance, of being a branched cell. Of course we 

 are equally at issue with him in his conception of a fixed cell of the 

 connective tissue, and believe that his "cellule plate" is only an 

 exhausted fat-cell, such as we have drawn in Figs. 9, 10, and 11 ; 

 and if anyone takes the trouble to compare our drawings with the 

 drawings given by Kanvier at page 3-10 of his ' Traite d'Histologie ' 

 of his " cellule plate " (of which we have seen the original), he will 

 see a wonderful identity between them, an identity which does not 

 stop with appearance, but is continuous even in the physiological 

 attributes he ascribes to it. 



All these considerations show how dangerously vague a term is 

 that of the connective tissue, and as we have already held that in 

 those divisions of it which we have been considering there are no 

 special fixed branched cells, it is clear that in our opinion no fat- 

 cells can be formed from them. 



The hypothesis advanced by Flemming that fat-cells are 

 developed from the branched cells of the adventitia of the blood- 

 vessels, seems to have met with general and, it seems to us, un- 

 merited condemnation, for we have evidently here only an error of 

 name and not of fact. 



In the first place, as Flemming is not responsible for the term 

 adventitia of blood-vessels, let us inquire what really constitutes this 

 adventitia. Anyone who studies silvered preparations of the skin 

 in mammals, cannot fail to be struck by the numerous and well- 

 marked branched ceils which lie specially upon the veins forming 

 their so-called adventitia and stretching out from them for a con- 

 siderable distance into the neighbouring gelatinous matrix, or, as it 

 is called, white fibrous tissue. 



The number of these branched cells seems to be considerably 

 afiected by various pathological conditions, so much so that we feel 

 unable to admit that they are anything else than wandering cells 

 clustering about the vein as if they were either about to enter or to 

 leave it. 



That fat should be developed in such wandering cells lying in 

 so close proximity to nutrition, is not only reasonable, but in general 

 accordance with our observations ; for, as a matter of fact, fat-cells 

 in a fat-tract found close to the lines of blood-vessels, seem to be 

 developed from the wandering cells nearest to the vessel, and which 

 would probably be called cells belonging to the adventitia of the 

 vessel. 



In Fig. 5 we have an illustration of the manner in which a fat- 

 tract extends along a blood-vessel. In the cells there shown, the 

 fat seen within them had been deposited to our certain knowledge 

 within a period of twenty-four hours, and, although deposited in 



