ON THE MORBID STATES DENOMINATED PNEUMATOSES. 103 
vegetable kingdom, whence is effected the reduction of the 
oxyde ingredients of the air to serve the purposes of the forma- 
tion and repair of organization. 
So that modern chemistry has traced with admirable pro- 
fundity the important part performed by the air, the grand 
agent, this immense reservoir, which, by itself or through the 
agency of the substances contained in it, furnishes the primary 
elements of vegetable organization. Here, then, is the primi- 
tive form of the constituent elements of living bodies (to wit), the 
gaseous state. It is likewise through the same state that 
comes their end. 
But it is not only at their formation, or at their decay, that 
their immediate principles become resolved into gas: the same 
thing happens in the course of their lifetime. Even in their 
very tissues gas becomes developed, and commonly as the pro- 
duct of secretion ; only such products are not generated in any 
continuous or permanent manner, like carbonic acid gas exhaled 
by the green parts of vegetables : they form but under certain 
conditions and for certain uses, which we shall now consider. 
M. de Blainville, in his General Physiology (vol. iii, p. 124), 
is of opinion that there are two kinds of principal gases : one to 
be accounted elementary, composing the integrant part of the 
organism, which exists constantly and normally ; the other, as 
I have just remarked, secreted or exhaled by the tissues. 
The elementary gases, observes this learned physiologist, enter 
into the composition of the body, are found in the cells of the 
tissues, and through them distributed over every part of the 
body. The physical characters of these elements become con- 
founded with the anatomical character of the tissues, so that 
they are only to be found in the component solids of organization : 
we may add, or in liquids , since it is beyond all doubt that the 
blood contains among its molecules particles of aeriform fluid. 
And gaseous products are, like other products of the body, 
according to the same author, substances differing in nature, 
disposed about the orgasm, oftenest upon the surface of the 
body (meaning by surface not only the skin, but the different 
mucous inlets, all corresponding to the exterior as well), but 
sometimes likewise within certain cavities and cells, without, 
in fact, composing part of their organism, and which may, with- 
out disturbing them, be extracted from them, or may be rejected 
by them. 
Gaseous products appear to be the result of secretions analo- 
gous to those producing fluids. Like as the skin furnishes the 
perspirable matter, it produces likewise carbonic acid gas ; and 
the mucous passages of the bronchi give issue not only to car- 
bonic acid gas, but likewise to azote and to water. Gland* 
