THE MICROBES OF HUMAN DISEASES. 189 



The same observer was able to point out the spores, 

 which are only visible under a magnifying power 

 of 1000 diameters, and which succeed to the spirilla 

 during the remittent period. Moreover, a monkey was 

 successfully inoculated with the disease at Bombay, 

 and after the lapse of five days spirilla were found 

 in the animal's blood. 



Yellow fever has not yet been sufficiently studied 

 in the countries in which it prevails, but there can 

 be no doubt that it is likewise produced by a special 

 schizophytum. Originating, as it appears, in North 

 America, probably in the delta of the Mississippi, this 

 disease has been spread by maritime commerce over 

 the whole intertropical zone of the globe. The centres 

 of infection are always on the sea-board, at the mouths 

 of great rivers, from which we conclude that its special 

 microbe is found in its free state in the brackish 

 marshes formed at river-mouths. 



The medical men of Rio de Janeiro, and particu- 

 larly Freire, have lately described and published illus- 

 trations of microbes said to have been observed by 

 them in the faeces of patients attacked by yellow 

 fever. But their drawings are for the most part 

 fanciful, and betray great inexperience in the methods 

 of research and in microscopic examinations; for 

 instance, the air-bubbles, unskilfully interposed in 

 the preparations which their author thought worthy 

 of photographic reproduction, figure as microbes. 

 Thanks to the accuracy of photography, which leaves 



