Discussion on Sanitation. 51 



been shown that microbes pass off in excrementitious matter, so 

 that we should naturally expect to find them in the sewers, and, 

 as a matter of fact, we do so find them. But persons who have 

 investigated the subject have found that the sewer gas, at any 

 rate, is freer from the spores of these microbes than the ordinary 

 air. There are methods by which not only the spores can 

 be detected, but their numbers measured ; — by applying this 

 ingenious test the fact I have referred to was discovered, and it 

 is proved beyond doubt that the air of the sewer is freer from 

 microbe spores than the ordinary air outside. I cannot reconcile 

 this statement with the undoubted fact that sewer gas causes 

 disease. I will leave it to the audience to do that. At present 

 we are right in placing some reliance upon theories, but very 

 much more upon experience, and I will say that, whether it 

 may contain few microbes or many, and although we do not 

 know in what way it acts to produce disease, we are quite 

 justified in endeavouring to keep sewer gas out of our houses. 

 (Dr. Letts then exhibited a number of glass models of appliances 

 for trapping drains, &c, and performed a number of experiments 

 illustrating their action.) 



The Chairman then called upon 



Dr. Calwell, who spoke on the relations of micro-organisms 

 to disease. He said : — The microbe theory has revolutionised 

 our ideas of disease altogether. It is known that a large amount 

 of disease is avoidable, especially diseases which are caused by 

 micro-organisms. First of all, we have the class of disease which 

 is caused by micro-organisms, and in that is included tuber- 

 culosis. Consumption, blood poisoning, and some diseases 

 which occur among cattle and sheep, as Pasteur has discovered, 

 belong to it. It has been proved that the dust on the walls and 

 floor of a room inhabited by a person who has died of con- 

 sumption is able to cause tubercular disease in animals. The 

 second class of disease to which I will refer is typhoid, scarlatina, 

 and certain forms of inflammation of the lungs. It seems 

 probable that in time we shall demonstrate that these diseases 

 are caused by micro-organisms although this has not yet been 



