DISEASE GERMS. 



157 



It is well known that many contagious diseases 

 may be propagated by the breath. Of this we have 

 direct proof as regards the poison of cattle plague, 

 small-pox, scarlet fever, and some others. Kiichen- 

 meister made a sheep breathe, during one hour, air 

 which was made to traverse the shirt worn for twelve 

 hours by a patient who was suffering from small-pox. 

 Five days afterwards the disease commenced, and by 

 the eighth day a well-marked eruption of variola 

 was developed upon the sheep. Glanders is another 

 contagious disease, and of a most fatal kind, which 

 is propagated through the air, and, although direct 

 inoculation is usually necessary for its communication 

 to man, in one case which fell under my observation, 

 the evidence that the fatal disease was communicated 

 by the air was very strong indeed, if not perfectly 

 conclusive. 



I have endeavoured to ascertain if such particles 

 as I have described could be actually demonstrated 

 by microscopical investigation with the aid of the 

 highest powers, in the air which was known to 

 contain a form of contagious poison. Mr. Crookes 

 made some investigations upon this part of the 

 subject in connection with the Cattle Plague Inquiry, 

 and he obtained some very interesting and important 

 experimental results. He was good enough to give 

 me a tube which contained a piece of cotton wool 

 that had been exposed to the breath of a diseased 

 animal, and was fully impregnated with contagious 



