120 BACTERIOLOGY. 



effusions, can also be employed after sterilisation in the steam 

 steriliserj The fluid should be withdrawn with a sterilised trocar 

 and cannula, and received into plugged sterilised flasks. 



Urine. — In order to obtain urine free from micro-organisms the 

 following precautions must be observed : The orifice of the urethra 

 must be thoroughly cleansed with weak carbolic. The first jet of 

 urine should be rejected, and the rest received into sterilised vessels, 

 which must be quickly closed with sterilised plugs. If these pre- 

 cautions be not attended to, the urine must be rendered sterile by 

 the means described for the sterilisation of broth. 



Milk. — If milk has been drawn into sterile flasks, after thoroughly 

 cleansing and disinfecting the teats and hands, it may be kept 

 without change. If procured without these precautions, it must 

 be steamed in the steriliser for half an hour for five successive 

 days. 



Vegetable and other Infusions Infusions of hay, cucumber, 



and turnip are used for special purposes, and more rarely decoctions 

 of plums, raisins, malt, and horse-dung. They are mostly prepared 

 by boiling with distilled water, after maceration for several hours. 

 The filtrate is received into sterile flasks and sterilised in the usual 

 way in the steam sterihser. 



Artificial Fluids. — Pasteur's solution is prepared by mixing the 

 ingredients in the following proportions : — 



Distilled water . 100 



Pure cane-sugar 10 



Ammonium tartrate . 1 



Ash of yeast . . -075 



Mayer's modification of the nourishing fluid employed by Cohn is 

 as follows : — 



Distilled water . 20 



Ammonium tartrate . -2 



Phosphate of potassium . . -1 



Sulphate of magnesium -1 



Tribasic calcium phosphate . -01 



Drop-cultures — This method of cultivation is a particularly 

 instructive one. It enables us to study many of the changes which 

 take place during the life history of micro-organisms. This is 

 illustrated, for example, in a drop-culture of the anthrax bacillus, 

 in which we can watch the gradual growth of a single bacillus into 



