226 



THE SOLIDS. 



Such are the facts hitherto recorded in favour of the pre- 

 sence of a nucleus in the fat vesicle : it will be seen that 

 although they are more definite and satisfactory than those 

 adduced in proof of the existence of an investing membrane, 

 yet that they are scarcely in themselves sufficient to set at 

 rest the question of its cellular nature. 



The observations then cited above, while they fail to de- 

 monstrate sufficiently the true organisation of the fat vesicle, 

 yet render it extremely probable that it is really cellular. 

 In favour of this view, a few additional observations have 

 occurred to myself, which are conclusive on one of the two 

 debated points of the organisation of the fat vesicle. The first 

 have reference to the outer membrane. If a thin slice of any 

 of the softer fats placed between two plates of glass be 

 pressed firmly, though not with too great violence, and sub- 

 sequently be examined with the microscope, it will be seen 

 that the vesicles have not run into each other, but still pre- 

 serve their individuality. 



Again, ether applied to the fat vesicle does not entirely 

 dissolve it ; even when it causes it to burst and collapse, a re- 

 sidue always remains, and this probably is membranous. 



Furthermore, if a thin slice of fat be placed between two 

 plates of glass, and having been forcibly compressed, be exa- 

 mined with the microscope, it will be seen that some of the 

 vesicles have burst, discharging a portion of their contents, 

 the membrane of the fat vesicle then becoming visible, and 

 declaring its existence by certain folds and markings, into 

 which it falls on the escape of its contents, and by the jagged 

 outline of the rent through which those contents passed. 

 (See Plate XIX. fig. 2.) 



Finally, decomposition produces an effect somewhat ana- 

 logous to that occasioned by pressure ; the fat vesicles burst, 

 and their fluid contents escape, leaving the membrane in 

 most cases entirely empty, and which, as well as the aperture 

 in its parietes, may be easily detected with the microscope ; 

 the soft contents of- the vesicles break up and resolve them- 

 selves into globules of an oil-like appearance. (See Plate 

 XIX. fig. 4.) 



