POTATOES 51 



Fresh eggs are cleansed with soda solution, washed, and 

 laid in corrosive sublimate, which must be removed with 

 ammonium sulphide, spirit, and ether before they are 

 inoculated. The latter is done by piercing the apex with a 

 needle which has been sterilised at a glowing heat, and 

 introducing the seed material into the interior by means 

 of a glass capillary tube, from which it is carefully blown 

 out as the tube is withdrawn. Closure is then effected 

 with sterilised cotton-wool or collodion. This method is 

 particularly well adapted for the cultivation of anaerobes. 



Potatoes. — An excellent culture material for the different 

 micro-organisms, and one, moreover, which secures their 

 development in a quite characteristic way, is the potato. 

 This medium is prepared as follows, according to Koch's 

 method : — The potatoes are carefully cleaned in water with 

 a brush, and after being freed from dirt are laid for half an 

 hour in a 1 per 1,000 solution of corrosive sublimate to 

 which some -g per cent, hydrochloric aicid has been added, 

 and finally washed with water to remove the adherent sub- 

 limate. With the aid of a sterilised knife single specks of 

 dirt and ' eyes ' are removed from the surface of the potatoes, 

 which are next heated for about an hour in the steam 

 apparatus and then cut into halves with a sterilised knife, 

 when the free cut surface of each of the halves can be 

 utilised for the culture of micro-organisms. If it is desired 

 to ascertain whether the potatoes are perfectly sterilised, 

 several of those treated as above can be left in moist 

 chambers and watched to see whether micro-organisms 

 develope, in which case the process of sterilising in the 

 steam apparatus must be repeated. 



If the potatoes after being washed in water, disinfected 

 in corrosive sublimate, and carefully cleaned on the surface, 

 are cut into several rather thick discs which fit into small 

 sterilised boxes of glass, each individual disc can be used as 



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