ANAEROBIC CULTURE 93 



For large flasks, the lateral tube may be just bent down 

 and a little capsule of mercury attached. 



The addition of J to 1 per cent, of sodium formate to 

 the culture media much simplifies anaerobic cultivation ; 

 the tetanus bacillus, for example, can be grown in formate 

 broth in a stoppered bottle without any elaborate pre- 

 caution for excluding the last traces of air. The sodium 

 formate should be added immediately before the last 

 sterilisation, not previously, or decomposition may occur. 

 Sodium sulphindigotate (0-3 per cent.) may be similarly 

 used. 



With such a broth, Dean's bottle may be used for 

 anaerobic cultivation. This consists of a bottle around 

 the neck of which a gutter for mercury is formed. A 

 glass cap loosely fits over the mouth of the bottle, and its 

 edge dips into the mercury in the gutter, thus sealing the 

 bottle but allowing the escape of gas. 



Isolation of Organisms 



If the organism be present unmixed with other organ- 

 isms, and provided it will grow on culture media, there is 

 no difficulty in obtaining pure cultures by inoculating 

 tubes of the appropriate medium with a little of the 

 material. This is frequently the case in many diseases, 

 and by culturing from the blood or tissues pure cultures 

 may be obtained. 



As regards appropriate media, these must be adjusted 

 to the food requirements of the particular class of organ 

 isms to be cultivated. Thus for pathogenic organisms 

 of animals, media rich in protein are generally required, 

 e.g. blood serum, nutrient agar, gelatin and broth, etc. 

 For the organisms of plant diseases, vegetable infusions 

 of the plant itself or from other sources, with or without 

 the addition of vegetable proteins and carbohydrates, 



