1 66 MANUAL OF BACTERIOLOGY. 



infection by the pus-producing bacteria and the bacillus 

 tuberculosis. Dr. Roswell Park believes that prolonged 

 anesthesia makes patients who have undergone operations 

 more liable to surgical infections, and that absorption of 

 bacterial poisons and auto-intoxication due to the products of 

 disordered metabolism of the patient's own cells, predis- 

 pose to infection. Some of the above-mentioned conditions 

 can be imitated in laboratory experiments. Hens in a nor- 

 mal condition are not susceptible to the anthrax bacillus, but 

 Pasteur succeeded in making them contract anthrax 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 ex- 

 haustion produced by making them run a treadmill, and 

 pigeons by starvation. 



Abbott found " that the normal vital resistance of rabbits 

 to infection by streptococcus pyogenes is markedly dimin- 

 ished through the influence of alcohol, when given daily to 

 the stage of acute intoxication." It was less noticeable for 

 bacillus coli communis, and not observed for staphylococcus 

 pyogenes aureus. Pigeons and other animals have been 

 made susceptible to anthrax by intoxicating doses of alcohol. 



Climate and altitude appear to influence the liability to 

 infection with the tubercle bacillus, which occurs less com- 

 monly in Colorado and some other elevated regions than 

 in lower and more densely populated districts. 



Age. In general, infants are more susceptible to infec- 

 tions than adults, though apparently nearly exempt from 

 the exanthematous fevers during the early weeks of life. 

 Osteomyelitis is commoner in infants than in adults, as also 

 is tuberculous meningitis. 



How much influence is to be ascribed to individual pre- 

 disposition in contracting or warding off infection is unccr- 



