BACTERIA IN DISEASE. 179 



the anthrax bacillus, but Pasteur succeeded in making them 

 susceptible to this disease by artificially cooling them. Frogs, 

 on the other hand, which also are resistant to anthrax, may be 

 made susceptible by keeping them at an abnormally high 

 temperature. Rats were made more susceptible to anthrax 

 by physical exhaustion produced by making them run a tread- 

 mill and pigeons by starvation. 



Abbott found "that the normal vital resistance of rabbits to 

 infection by streptococcus pyogenes is markedly diminished 

 through the influence of alcohol, when given daily to the stage 

 of acute intoxication." This effect of alcohol was evident to a 

 marked degree with the anthrax bacillus, but it was less notice- 

 able for bacillus coli communis, and not observed for staphylo- 

 coccus pyogenes aureus. 



Climate and altitude appear to influence the liability to 

 infection with the tubercle bacillus; for, as everyone knows, 

 tuberculous affections occur less commonly in elevated regions 

 than in lower and more densely populated districts. 



There are probably a great many other as yet obscure con- 

 ditions affecting predisposition to infection. 



Age. — In general, infants are more susceptible to infections 

 than adults, though apparently nearly exempt from the exan- 

 thematous fevers during the early weeks of life. Osteomye- 

 litis is commoner in infants than in adults, as also is tubercu- 

 lous meningitis. 



Individual Predisposition. — The influence of individual 

 predisposition is often very marked; though, as Welch says, 

 "The fact that some individuals are attacked and others, ap- 

 parently equally exposed to the danger of infection, escape, 

 is not always due to any especial predisposition on the part of 

 the former. It may be that the germs hit the one and miss the 

 other, and we would have no more right to say that the former 

 are especially predisposed than to say that those who fall in 

 battle are predisposed to bullets and those who escape are 



