292 LIGHT SCIENCE FOR LEISURE HOURS. 



Take cholera, for example. It has been shown by the 

 clearest and most positive evidence that this disease is 

 not propagated in any way save one that is, by the 

 actual swallowing of the cholera-poison. In Professor 

 Thudichum's masterly paper on the subject in the 

 Monthly Microscopical Journal it is stated that doc- 

 tors have inhaled a full breathing from a person in 

 the last stage of this terrible malady without any evil 

 effects. Yet the minutest atom of the cholera-poison 

 received into the stomach will cause an attack of chol- 

 era. A small quantity of this matter drying on the 

 floor of the patient's room, and afterward caused to 

 float about in the form of dust, would suffice to pros- 

 trate a houseful of people. We can understand, then, 

 how matter might be flung into the streets, and, after 

 drying, its dust be wafted through a whole district, 

 causing the death of hundreds. One of the lessons to 

 be learned from these interesting researches of Mr. 

 Dancer is clearly this, that the watering-cart should 

 be regarded as one of the most important of our hygi- 

 enic institutions. Supplemented by careful scavenger- 

 ing, it might be effective in dispossessing many a ter- 

 rible malady which now holds sway from time to time 

 over our towns. 



(From the Daily News, March 6, 1869.) 



