

CULTURAL CHARACTERISTICS 



317 



of 6 per cent, glycerin-agar melted in a water bath and kept at 50 C. The 

 ingredients are mixed as thoroughly as possible and the tubes allowed to set 

 in a sloped position. From human lesions, moist, greasy-looking colonies 

 can be obtained in a week on this medium. 



Phisalix prepares a medium by mixing yolk of egg with a potato mash 

 containing a little glycerin. The medium is sterilized in the autoclave. 

 Lubenau gives a method which has already been described (p. 54). 



According to Park, yolk of egg media are particularly useful for the isola- 

 tion of tubercle bacilli 'from tuberculous material and for the differentiation 



of the human from the bovine type. 



On media made with yolk of egg but 

 containing no glycerin bacilli of the 

 bovine type grow easily : and on the 

 same media but containing glycerin 

 bacilli of the human type grow poorly 

 at first while the bovine type does not 

 grow at all. 



[According to A. S. Griffith (English 

 Commission) the egg medium is in- 

 valuable for obtaining the tubercle 

 bacillus in pure culture from tissues or 

 other material. It is of great value also 

 for sub-cultures ; on it the tubercle 

 bacillus retains its vitality for a longer 

 period than on any other medium, and 

 sub-cultures can often be obtained on 

 this medium from old cultures which 

 fail to grow when sown on other media. 

 He gives the following method of pre- 

 paration of the medium " The yolk and 

 the white of fresh eggs are thoroughly 

 mixed by shaking in a flask ; salt solution 

 is added in the proportion of one to three 

 of egg ; the mixture is filtered through 

 muslin, distributed into tubes, sloped and 

 coagulated in a serum inspissator at 

 80 C."] 



4. Blood-agar. -Bezancon and Griffon 

 recommend the addition of rabbit-blood 

 to agar for starting cultures from human 

 or animal tissues. Growth appears early 

 and soon becomes very copious, the 

 colonies absorb the haemoglobin and 

 become chocolate-coloured. 



5. Tochtermann's agar. Dissolve 10 grams of peptone, 5 grams of sodium 

 chloride, 5 grams of glucose and 20 grams of agar in a litre of water. Add 

 half-a-litre of calf serum, mix, boil for 15 or 30 minutes, filter in the warm, 

 distribute into tubes and sterilize at 100 C. for 50 minutes. 



6. Hesse's agar. For obtaining cultures of the tubercle bacillus from human 

 sputum Hesse recommends sowing the material on the surface of a special 

 agar prepared as follows : 



Dissolve 5 grams of salt, 30 grams of glycerin, and 20 grams of agar in a 

 litre of water. Add 5 c.c. of a normal solution of carbonate of sodium and 5 

 grams of Heyden's albumose (Nahrstoff Heyden) dissolved in 50 c.c. of water. 



(a) (6) 



FIG. 208. Primary cultures of tubercle bacilli 

 on the egg medium . (a) Bovine tubercle bacilli 

 of human origin obtained direct from sputum 

 bv means of antiformin : (6) Human tubercle 

 bacilli (A. S. Griffith). (See footnote p. 316.) 



