106 ON THE MORBID STATES DENOMINATED PNEUMATOSES. 
he has never seen globules of air escape from the body of the 
foetuses which he has opened under water. Notwithstanding 
this imposing authority, however, one is tempted to doubt the 
correctness of the assertion, when one knows that the blood of 
the mother and the waters of the amnion both contain gas. 
(B.) Of the Gases of the Generative or Cellular Tissue. 
The presence of gas in the cellular tissue is abundantly 
proved by the formation of emphysema, at times very con- 
siderable. 
We find them within the cellular tissue entering into the 
composition of organs, as well as in that which forms the ad- 
herent surface of serous and ligamentary membranes. 
Underneath the skin, emphysema, in some cases, makes its 
appearance spontaneously, or without any appreciable cause : 
it then seems to be the result of a particular and entirely local 
secretion of this tissue. More commonly, however, the accu- 
mulation of sub-cutaneous gases depends upon some internal 
morbid condition, of which it is but the effect or a symptom. 
Fevers called adynamic and typhoid, and typhus fever, and the 
introduction through the skin of certain poisons, furnish exam- 
ples of this. 
But the presence of aeriform fluids underneath the skin, con- 
stituting emphysema, is at times purely accidental ; it may de- 
pend 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 organs, 
especially of the lungs, it no doubt owes its presence to respira- 
tion, which escapes through some laceration or perforation of 
some of the air-cells, previously dilated and softened by the 
action of inflammation. 
It is the same with the gases found in the sub-pleural cellular 
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 by Serous Membranes 
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 contains 
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. 
