TEGUMENTAL SYSTEM. 415 



cells or small cavities : and this it was that first gave rise to the 

 name of cellular membrane. These cells have a free communi- 

 cation with each other ; a fact demonstrated by occurrences of 

 the most common' and familiar kind : who has ever seen the 

 carcass of a calf inflated by a butcher, in order to give the veal a 

 fatter and whiter aspect, will need no farther proof. There are 

 many phenomena, however, connected with disease, that verify 

 the same thing: in emphysema (which is a swelling of the skin 

 in consequence of the admission of air through a wound com- 

 municating with the cells of this membrane), the air very com- 

 monly diffuses itself over the whole body ; and a wound in the 

 chest, or one at the point of the elbow, is the most likely of any 

 to be followed by such consequences. Again, in anasarca 

 (which is an effusion of water into this substance), or in ecchi/- 

 mosis (an extravasation of blood into it), the fluids invaria- 

 bly, after a time, occupy the most depending parts : hence the 

 tumefaction of the legs, breast, belly, and shtath, in the first of 

 these diseases, beyond that of any other parts. 



Exhalation. — Into the cells of this mcDibrane, during life, is 

 poured forth a serous fluid, in the form of vapour, by the ex- 

 halent extremities of the arteries; from the exhalation of which, 

 that peculiar odour so constantly perceived in flaying an anin)al 

 recently dead is emitted. 



Modification. — In addition to the modified forms of this mem- 

 brane already noticed, one yet remains to be mentioned. In 

 most structures it is opaque, but there is one part where its 

 texture is so very fine and delicate, that it is perfectly transpa- 

 rent : it is the tunica vitrea in the eye, through which the rays 

 of light pass without the slightest interception. 



Elasticity. — The cells of this membrane possess a degree of 

 elasticity. If, for instance, we include a portion of skin between 

 our finger and thumb, it will suddenly recoil on being liberated, 

 and recover its original situation; a circumstance in part 

 attributable to the elastic property of the subjacent cellular 

 membrane. 



Organization. — The cellular membrane is not very vascular : 

 the bloodvessels found ramifying within it being chiefly dis- 

 tributed to other and neighbouring parts ; so that whenever 

 violent inflammation is excited in it, sloughs of it not uncom- 

 monly take place. This happens when we introduce any caus- 

 tic under the skin ; the core which comes out being chiefly 

 dead cellular membrane. Absorbents would seem to exist in 

 great numbers in it ; for if we but extravasate quicksilver under 

 the skin, in some parts of the body, it will find its way through 

 the cells of the cellular membrane into many of these vessels. 



