TYPHOID FEVER. 201 



made use of solutions of alum, bichromate of potash, 

 Bismarck brown, fuchsine, methyl blue, gentian violet, &c. 

 He found that the yellow and brown solutions filtered out 

 the chemical rays and prevented the action of light upon 

 the organisms almost as efficaciously as the black and white 

 papers, but found that the other fluids — fuchsine, methyl 

 blue, gentian violet, &c. — had little more effect in preventing 

 the injurious action of light on the bacilli than distilled 

 water or alum solution. He therefore comes to the con- 

 clusion that the hurtful action of both diffused light and 

 direct sunlight is due in very great measure to the chemical 

 rays of the solar "spectrum — ^the rays at the other end of 

 the spectrum exerting comparatively little influence on the 

 organism. This entirely accords with Englemann's observa- 

 tions ; he found that certain chromogenic bacteria when 

 examined in a drop of water and illuminated by the rays 

 from a micro-spectral objective, invariably made their way to 

 that part of the spectrum furthest away from the violet end, 

 thus indicating that they were attempting to evade the 

 chemical rays which appeared to be hurtful to them. This 

 question of the action of light, especially on pathogenic 

 bacteria, is one of very great importance, and Duclaux's 

 dictum that fresh air and sunlight are two of the most 

 powerful agents that we have with which to combat the 

 onslaught of the bacteria of disease cannot be too strongly 

 insisted upon. Bacteria, especially those of disease, seek out 

 the dark places for their habitation, and as the exclusion of 

 light to a very great extent necessitates the exclusion of fresh 

 air, they find in these holes and corners places of rest whence 

 they may go out to do all the harm of which they are 

 capable. 



Janowski also made an elaborate series of experiments on 

 the effect of high temperature on the typhoid bacillus. He 

 found that a temperature of 55° C. continued for ten minutes 

 was quite sufficient to render sterile cultivations of this 

 bacillus, but if this same temperature were continued for 

 only five minutes he could not rely upon obtaining complete 

 destruction of the organism. He also came to the conclusion 

 that an extreme degree of cold, especially when continued 

 for some time or where frequently repeated, had a moderately 

 injurious effect upon the vitality of the typhoid bacillus ; a 

 temperature of 14° C. being sufficient to kill the bacilli when 



