48 THE NATURE AND TREATMENT OF 



continuous or permanent manner, like carbonic acid gas ex- 

 haled 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 

 1 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 

 confounded with the anatomical character of the tissues, so that 

 they are only to be found in the component solids of organiza- 

 tion ; 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 organism, 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 with many without 

 disturbing them, be extracted from them, or may be rejected 

 by tliem. 



" Gaseous products appear to be the result of secretions anal- 

 ogous to those producing fluids. Like as the skin furnishes the 

 perspirable matter, it produces likewise carbonic acid gas ; and 

 the mucous passages of the bronchii give issue to not only car- 

 bonic acid gas, but likewise to azote and to water. Glands 

 also, it is probable, secrete gas with their habitual fluids ; and 

 the cellular tissue itself generates gas in the case of emphysema, 

 as well as serosity, and so likewise do serous surfaces. 



" These general positions established, without stopping to in- 



