CHAPTER X. 

 EFFECT OF OTHER AGENTS ON BACTERIA. 



Radium Rays. Fernan and Pauli have shown that the exposure 

 of proteins (serum albumin) in acid or alkali solution to radium 

 radiations causes their coagulation. It is well known that the expos- 

 ure of living tissue to these rays cause their destruction, and attempts 

 have been made to treat certain bacterial diseases by their use, but 

 so far without any great degree of success. The sterilization of milk 

 and other foods by this method has been suggested, but its practical 

 application appears to be improbable on account of the cost and 

 uncertainty of the results. 



The fixation of elementary nitrogen by A. chroococcum is dis- 

 tinctly increased when the air is activated by pitchblend, somewhat 

 better results being obtained with weak than with stronger radio- 

 active intensity. Attempts have been made to force higher plants 

 by its use, but so far without any practical success. 



Rontgen Rays. Although rontgen rays are used in the treatment 

 of microbial diseases of the scalp and skin, it has been conclusively 

 shown that they are not even inhibitory, let alone fatal to the cells. 

 This is seen from the results by Zeit, who found that bouillon 

 and hydrocell-fluid cultures in test-tubes of non-resistant forms of 

 bacteria Was not killed rontgen rays after forty-eight hours' ex- 

 posure at a distance of 20 mm. from the tube. Tubercular sputum 

 exposed to these rays for six hours at a distance of 20 mm. from the 

 tube caused acute miliary tuberculosis of guinea-pigs inoculated 

 with it. The hopes that were entertained of being able to disinfect 

 the diseased body by this means have not been realized. The clinical 

 results which are sometimes obtained must be explained by factors 

 other than their direct germicidal influence, possibly by the pro- 

 duction of ozone, hypochlorous acid, extensive necrosis of the deeper 

 layers of the skin and phagocytosis. 



Electricity. The influence of electricity itself upon micro- 

 organisms is probably very slight, but it is often difficult nicely 

 to differentiate between purely electrical effects and chemical 

 changes which are produced in the media by the electric current. 

 A direct current passing through a nutrient medium will cause an 

 electrolysis which is usually manifest by the generation of acid on 

 the positive electrode and alkali on the negative. The passing of 



