TRANSACTIONS OF THE SECTIONS. 121 
same time convinced that its cultivation would in turn accelerate the progress 
of general science. A very little reflection will suffice to demonstrate that, under 
the general term “ organic effluvia,” several entirely distinct substances have been 
confounded; and as it is impossible to entertain any clear ideas of their action 
as causes of disease, without greater precision in this respect, I am induced to 
direct attention to the subject. The importance of a clearer classification will 
be manifest when we consider that our arguments and inquiries respecting epi- 
demic diseases must be materially influenced by the views prevalent as to the 
composition, properties, and affinities of those peculiar matters present in the 
vatmosphere, which form the basis of such pathological and hygienic researches. 
In the present state of our Imowledge, I am inclined to think that all those 
abnormal constituents of the atmosphere which are recognized under the gene- 
ral term “organic eflluyia” may be resolved into four principal groups, viz. :— 
1. Gases and the vapours of volatile chemical compounds formed during the de- 
composition of organic matter. 2. Odoriferous particles sui generis. 3. Volatile 
organic matters not endowed with vitality. 4. Living germs. 1. In the first 
oup I would place not only the binary gaseous compounds evolved, for instance, 
uring putrefaction, such as the compounds of hydrogen with sulphur, phosphorus, 
carbon, &c., but also ammonia and its curious combinations with sulphur and phos- 
phorus, described by Dr. Crace Calvert as formed during the decomposition of 
animal matter. 2. The natural philosophy of odours is so little known that no 
excuse need be offered for placing in a separate group the volatile particles capable 
of being detected by the sense of smell, but not demonstrably related to any known 
gases or vapours. 38. The third class of organic effluvyia is one to which I attach 
great importance from the belief that not only are those volatile organic matters 
often, perhaps generally, poisonous in themselves, but that they are also injurious to 
an incalculable extent by sheltering, nourishing, and so propagating the noxious 
germs liable at all times to be suspended in the atmosphere. And if it can be demon- 
strated that volatile organic matter is present, under certain circumstances, in the 
air surrounding us, there is no more difficulty in believing it capable of nourishing 
and contributing to the growth and development of contiguous germs, than in 
supposing the animalcules present in water to derive their chief support from the 
animal and vegetable matters dissolved or suspended in it. That organic matter is 
present in the atmosphere might at once be inferred from the varied odours pro- 
ceeding from plants and animals, and from the injurious effects exercised on 
living animals by exposure for a length of time to accumulations of such effluvia. 
But modern chemistry has converted this probability into a certainty. Vauquelin, 
on analyzing the liquid obtained by the decomposition of marsh deos, found in the 
residue an organic substance which blackened or charred on exposure to heat. 
Zimmerman has described, under the name of “ pyrrhine,” volatile organic matter 
universally present in rain and snow-water. And more recently Dr. Angus Smith 
has even determined the relative quantity of the organic constituents of the atmo- 
sphere present under different circumstances. This point may, therefore, be con- 
sidered as definitely settled. 4. The existence of living germs in the atmosphere 
is proved by the phenomena of what has been erroneously called “ Equivocal 
Generation,” such as the appearance of fungi on animal and vegetable substances 
secluded from everything but the atmosphere, air, &c. The possible dependence 
of epidemic diseases on the entrance into the blood circulating within the human 
body of some varieties of these organic germs is favoured by many analogies and 
bysome direct evidence. For instance, Dr. Robert Dundas Thompson, who examined 
the air contained in the cholera-wards of St. Thomas’s Hospital during the epidemic 
of 1854, states “that in the atmosphere of a cholera-ward ee rc dees were 
diffused throughout the air, derived from the inmates; that sporules of fungi, and 
germs of vibriones, or vibriones themselves, were obtained by filtration from the 
atmosphere.” In leaving this subject for the present, it may be well to observe, 
that whatever classification of these volatile invisible particles emanating from 
living or dead animal and vegetable matter may eventually be adopted, they are 
doubtless so mixed together as to render their separation in any definite quantity 
of air very difficult, if at all practicable, For instance, in the effluvia proceeding 
