170 MICEOBES, FEEMENTS, AND MOULDS. 



by contact "witli 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, 

 Nageli uses the word, he regards it as synonymous 

 with microbes or air-germs. 



TAe 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 

 ploTTib 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 



