80 LOCOMOTION. [CHAP. in. 



OF THE ADIPOSE TISSUE, AND OF FAT. 



This tissue has no alliance either of structure or function with 

 the areolar tissue; it is, however, usually deposited in connexion 

 with that tissue, and therefore we find it convenient to notice it 

 here. Malpighi, W. Hunter, Monro, and, more recently, other 

 distinguished anatomists, pointed out the distinctness of these two 

 tissues; but such has been the influence of the term cellular, ap- 

 plied to both, that they are still usually classed together. Now, 

 however, that microscopes, on which reliance can be placed, declare 

 their totally distinct nature, it is full time that they be treated of 

 as altogether distinct and independent tissues. 



A common use of the adipose tissue being to occupy spaces of 

 various dimensions left in the interstices between organs, and thus 

 to facilitate motion and contribute to symmetry, it is very com,- 

 monly closely associated with the areolar tissue ; but the connexion 

 is not an essential one. In the cancelli of bones there is a large 

 deposit of fat, but none of this filamentary tissue ; and in numerous 

 situations, as the eyelids, beneath the epicranial aponeurosis, be- 

 tween the rectum and bladder, under the mucous membranes, and 

 in the whole of the cutis, the areolar tissue exists without being 

 ever accompanied by fat. Nevertheless, their apparent admixture 

 in many situations has given rise to the term "adipose cellular 

 tissue/' applied to the two combined, as distinguished from that 

 areolar tissue which contains no fat. This term should be dis- 

 carded, as leading to much misconception. 



A distinction is to be drawn between fat and the adipose tissue. 

 The tissue is a membrane of extreme tenuity, in the form of closed 

 cells or vesicles ; the fat is the material contained within them. 



The Membrane of the Adipose Vesicle does not exceed the 2 ooo~o ^ 

 an inch in thickness, and is quite transparent. It is moistened by 

 watery fluid, for which, as Mr. Paget has suggested, it has a greater 

 attraction than for the fat it contains. It is perfectly homogeneous, 

 having no appearance of compound structure, and consequently be- 

 longs to the class of simple or elementary membranes. Each vesicle 

 is a perfect organ in itself; is from the -j^ to the -g^ of an inch 

 in diameter, when fully developed ; and is supplied on its exterior 

 with capillary blood-vessels, having a special disposition. 



The fat vesicles are usually deposited in great numbers together, 

 and they then become flattened on their contiguous aspects, and 



