SYSTEMATIC STUDY OF SPECIES OF BACTERIA. 115 



at the same time. Moulds are easily obtained by exposing 

 some nutrient substance to the air, covering it, and allowing 

 cultures to develop; yeasts will probably grow also. Ordinary 

 brewer's yeast may be isolated in pure culture from gelatin 

 plates. Bacteriological examinations also should be made of 

 air, soil, water and milk. With such simple means, many of 

 the important properties of bacteria may be demonstrated. It 

 is most important that medical students should convince them- 

 selves by experiment of the extent to which bacteria are dis- 

 seminated in our environments. The bearings of such observa- 

 tions on the practice of surgery and hygiene are obvious. 



Experiments in sterilization and disinfection as described in 

 Chapter VIII., Part II., may be performed with the bacteria 



j mentioned, which present every variety of resisting power up to 

 the almost incredible resistance of the spores of the hay and 



potato bacilli. The efficiency of the methods used for steriliz- 

 ing surgical materials, as silk and catgut (Chapter IX., Part II.), 



j should be tested; also, of the methods for disinfectingthe hands, 



if possible, of the methods for disinfecting rooms, as well. 



After some proficiency has been acquired, various pathogenic 



i bacteria may be studied as the circumstances of the case re- 



| quire. Much judgment has to be used in allowing students 

 to work with pathogenic bacteria. Anthrax, glanders, tetanus, 

 cholera, bubonic plague, Malta fever, and diphtheria all have 

 occurred in laboratory workers through accidental infection, 

 sometimes with fatal results. Everything should be handled 

 with forceps as far as possible, and the forceps sterilized in the 

 flame before and after using. Particles of cotton fiber should 

 not be allowed to fly off from the plugs. The various rules 

 for the management of the platinum-wire, hanging-drop slides 

 and sputum bottles, and for the handling of cultures and other 

 infectious materials have already been given (pages 22, 23, 

 34 and 78 to 82). As the risks of infection from neglect of 

 proper caution are obvious enough, it would seem, that it 



