SYSTEMATIC STUDY OF SPECIES OF BACTERIA. 115 



used for sterilizing surgical materials, as silk and catgut 

 (Chapter IX., Part II.), should be tested; also, of the 

 methods for disinfecting the hands; if possible, of the 

 methods for disinfecting rooms, as well. 



After some proficiency has been acquired, various patho- 

 genic bacteria may be studied as the circumstances of the 

 case require. Much judgment has to be used in allowing stu- 

 dents 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. 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 33, 36, 44 and 84 to 88). The most important pre- 

 caution, perhaps, is observance of the rule that while work- 

 ing in the laboratory, nothing should be put in the mouth. 

 Cultures should never be carelessly left in improper places. 

 Cultures of bacteria should be thoroughly sterilized before 

 the tubes are cleaned. The writer is in the habit of having 

 tubes and dishes containing pathogenic bacteria placed in the 

 steam sterilizer for an hour on each of three days, and of 

 having the plugs removed and burned and the tubes filled 

 with 5 per cent, carbolic acid between the second and third 

 sterilizations. In taking these measures, the same kind of 

 reasoning applies as that which induces engineers to give 

 bridges from four to six times the strength they need to 

 bear the greatest strain likely to be put upon them, or to 

 make the boiler of a steam engine strong enough to bear 

 six times the greatest pressure which it is expected that 

 the steam contained in it will exert. 



