52 THE NATURE AND TREATMENT OF 



constituting emphysema, is at times purely accidental ; it may 

 depend upon a solution of continuity of the skin, permitting the 

 introduction of atmospheric air into the subjacent cellular 

 tissue. 



" As for the gas discovered within the parenchyma of or- 

 gans, especially of the lungs, it no doubt owes its presence to 

 respiration, which escapes through some laceration or perfora- 

 tion of some of the air-cells, previmisly dilated and softened 

 by the action of inflammation. 



" It is the same with the gases found in the sub-pleural cell- 

 ular tissue, and within the abdomen, in the peritoneal cellular 

 tissue, as the consequence of rupture or • perforation of the 

 stomach and intestines. 



" (C) The Reservoirs and Sacs formed hy Serous 3Iemhra7ies 

 are in some cases, normally/ or from morbid causes, the Seat 

 of Gaseous Collections. 



" Everybody knows that certain fish, such as carp and perch, 

 are provided with a reservoir called a swimming-bladder, placed 

 at the posterior part of the visceral mass. This reservoir con- 

 tains an aeriform fluid, which remains within it, and distends it, 

 and thus serves divers purposes to the animal. It is well known 

 that this gaseous fluid is not directly derived from the lung. 

 M. de Blainville assures us that the swimming-bladder has no 

 communication with the buccal cavity. He has never been 

 able to empty it through this passage, nor to force the gas out 

 through the respiratory channels. Indeed, the analysis made 

 of it by Messrs. Rumboldt, Proven9al, and Delaroche, has 

 shown that it is not directly furnished by the air of respiration, 

 but must be the product of a particular secretion. 



" The feathers of birds are, likewise, another example of air 

 reservoirs having no communication with the respiratory pa.s- 

 sages ; the air appearing to be introduced into them through 

 absorption, at the period when the gelatinous matters disappear, 

 which up to that time had filled the tubes. 



" We know that the air of respiration gains admission Into the 



