NATURE OF MATERIES MO RBI. 
323 
of syphilis, may be dried in the air without exhibiting any 
signs of volatility, tends to the contrary conclusion. If the 
matters of contagious diseases were of a volatile nature, they 
would evidently, by the law of gaseous diffusion, be liable to 
pervade the entire mass of the atmosphere in a form of 
extreme attenuation, not at all admissible from what we 
know of their effects. Volatility, moreover, w r hich implies 
simplicity of constitution and a limited number of atoms in 
the integrant particles of matter, would be incompatible with 
the organic character of such substances. We know that mere 
gases of the kind principally exhaled from persons suffering 
from fevers and other similar contagious affections, as ammo¬ 
nia, sulphide of ammonium, and such like, are of themselves 
insufficient to cause special disease w T hen breathed admixed 
with air. But as the vapours of volatile liquids carry with 
them sensible quantities of all the solids which are held in 
solution by them, the gases and exhalations given off from 
fever patients and their excreta are well suited for becoming 
the vehicles of non-volatile contagious matters, in the shape 
of consistent particles of complex matter analogous to the 
polybasic combinations of the organic kingdoms.* Being 
derived from the blood, these bodies may be presumed to 
exist in a peculiar state of active transformation, capable of 
communicating itself to the circulating fluid of other indi¬ 
viduals of the same species, when so circumstanced as to be 
unable to conduct their metamorphosis into simpler and 
more permanent forms. As they are clearly susceptible of 
increasing in activity and of propagating their condition, 
according to the circumstances in which they may be placed, 
they must also be capable of diminishing in morbid force, 
and of suffering resolution into a state of inertia by conver¬ 
sion into the last products of transformation. The progress 
of such matters will be regulated entirely by the opportuni¬ 
ties afforded them of meeting with active oxygen, which, 
whether in the process of combustion continually kept up 
within the body by the respired air, or in that which is as 
unceasingly in operation without, is the great means em¬ 
ployed by nature for the extinction of abnormal influences 
and the maintenance of sound sanitary conditions in the 
organic creation. 
if they do not consist merely of the usual organic sub¬ 
stances contained in bodily exhalations, brought into a 
peculiar catalytic state, those morbific matters at all events 
cannot be supposed to differ in constitution, in any material 
Graham’s ‘ Elements of Chemistry,’ p. 282 (1842). 
