THE PRESENT EVOLUTION OE MAN— PHYSICAL 237 



The purging -which accompanies the disease maj' 

 possibly quite clear the bowel of one recovering from 

 it of the bacilli, but after recovery such a one would be 

 as likely as any other again to swallow infected material, 

 when purging would not again occur; at least it has 

 not been found that persons recovered from cholera, 

 and immune to it, are liable to diarrhoea during an 

 epidemic, and that their discharges are infective. If 

 then an immune person swallowed infected material, 

 and if the contents of his bowel afforded all-sufKcing 

 nutriment, in which the bacilli were able to multiply 

 to an unlimited extent, his bowel would become the 

 home of a colony of bacilli, which, owing to the constant 

 renewal of their food supply, and the removal of their 

 waste products, would multiply perpetually, and would 

 perpetually infect his alvine discharges, to the danger 

 of the community ; unless indeed, which seems improb- 

 able, when we consider the enormous rate at which the 

 bacilli multiply, the churning movements of the intes- 

 tine so certainly brought all the bacilli within reach of 

 the phagocytes, now invulnerable to them, in the wall 

 of the bowel, that the latter were able to seize and 

 destroy them. But we know that no person who has 

 recovered from cholera ever becomes a source of per- 

 petual danger to the community, and we must conclude 

 therefore that, even if the bacilli are capable of multi- 

 plying to a limited extent in the non-living contents of 

 the bowel, that, unlike some harmless species of -micro- 

 organisms that normally inhabit it, they are not capable 

 of multiplying to an unlimited extent there, but must 

 periodically pass a time and find their nutriment in the 

 living tissues of susceptible individuals. 



The truth, therefore, appears to be, that the microbes 

 of cholera find their nutriment in the living tissues of 

 the host, but when the conditions of existence become 

 unfavourable there'—*, e. when the phagocytes react to 



