170 MICROBES, FERMENTS, AND MOULDS 
by contact with the men, nor by that with the 
clothes and baggage, which were mixed together. 
The cholera microbe which had been brought on 
board ship could only act on the detachment mias- 
matically predisposed by their previous residence in 
an unhealthy place, containing the malaria microbe 
(Nageli). 
Miasma and Microbes.—This leads us to say a few 
words on the term miasma, formerly in such common 
use, and now without meaning. Before the existence 
of microbes and air-germs was known, the doubtful 
and mysterious principles which were believed to be 
the cause of virulent and contagious diseases were 
termed miasmata, and these miasmata were generally 
supposed to be gases. It is now proved that this cause 
resides in solid, living particles, the microbes and their 
germs: the term miasma is less and less employed, 
or serves to designate air-germs. When, therefore, © 
Nigeli uses the word, he regards it as synonymous 
with microbes or air-germs. 
The Question of Privies—Hence it follows that 
it is erroneous to apply the name of miasmata 
to true gases, some of which exert an injurious in- 
fluence on the human system. Such are sulphuretted 
hydrogen and ammonium sulph-hydrate which are 
disengaged from privies, and produce the disease called 
plomb in the men employed to empty them. These 
gases are deleterious to microbes as well as to men; 
microbes cannot co-exist with them, which is perhaps 
