646 A MANUAL OF BACTERIOLOGY 



Failing this, the solutions may be made with the acidum carbolicum 

 liquefactum of the Pharmacopoeia, which contains 100 parts of 

 phenol in 110, but is not absolutely constant in composition. 



(3) All measu es, pipettes, and test-tubes used for making dilutions 

 should be sterile. 



(4) The dilutions of the disinfectant and carbolic should be made 

 with sterile distilled water. 



(5) The broth used for culturing and sub-culturing should have 

 the following composition : 



Lemco . . . . . .20 grin. 



Peptone . . . . .20 grm. 



Salt 10 grm. 



Water 1000 c.c. 



The medium should be standardised to a reaction of + 10 (Eyre's 

 scale). 



(6) The loop usecj for sulculturing should have an internal 

 diameter of 3 mm., and be made with platinum wire of 27-28 

 B.W.G. 



(7) Growths in the subcultures should be obtained in those taken 

 at not less than two and preferably at three of the time intervals 

 (2, 5, and 7 minutes) from both the disinfectant and the carbolic 

 solutions which correspond. 



(8) The temperature at which the determination is made should 

 be noted, and the strength of carbolic varied accordingly (1-100 

 for 56-62 F., 1-110 for 62-67 F., and 1-120 for 67-73 F. 

 for B. typhosus), or the determination may be made at a standard 

 temperature (e.g. 20 C.) by warming (or cooling) the disinfectant 

 and carbolic tubes in a water-bath. 



(9) When the organism does not form a uniform culture in broth, 

 a suspension of an agar or other culture must be made in water 

 and filtered. Sub-culturing in some cases (e.g. with B. pestis and 

 B. anthracis) must be made on agar or other suitable culture medium. 



The method is an admirable one for determining the relative 

 efficiencies of disinfectants on naked organisms in the absence of 

 organic matter. But in practice disinfection is almost always 

 carried out in the presence of organic matter, and various suggestions 

 have been made with a view of introducing this factor into the 

 test, for the presence of organic matter may reduce the carbolic- 

 acid coefficient of many disinfectants (see pp. 632-642, and Table, 

 p. 641). Among the substances suggested are urine, faeces, 2 

 per cent, suspension of dried and sterilised faeces (Martin and Chick), 

 and milk. Kenwood and Hewlett found that the presence of urine 



