224 MILK AND THE PUBLIC HEALTH CHAP. 



the tubercle bacillus is isolated from the lesions in the guinea- 

 pig. The primary isolation may be upon blood serum, or 

 preferably upon Dorset's egg medium. After one or several 

 generations of growth upon the egg medium subcultivations 

 are made upon glycerine agar and in glycerine broth. If no 

 growth takes place upon glycerine agar, as may be the 

 case with the bovine type, further generations are grown 

 upon the egg medium, and growth again tried upon glycerine 

 agar. For the inoculation of rabbits Weber l recommends 

 that two should be inoculated, one with 1 e.g. of culture 

 subcutaneously and the other with 1 m.g. intravenously. 



The egg medium may be prepared as follows : 2 Fresh 

 eggs are washed and then partially sterilised by dipping them, 

 held in forceps, in boiling water for about half a minute. 

 They are opened with aseptic precautions, and the contents 

 poured into a sterile flask, to which normal saline is added 

 in the proportion of one part to two parts of egg. The eggs 

 and saline solution are thoroughly mixed in the flask, which 

 should be of large size. The medium is strained through 

 muslin to remove air-bubbles, and poured as quietly as possible 

 into a flask with a side tube near the bottom. The medium 

 is added from this flask to the sterile test-tubes when the latter 

 are in a nearly horizontal position, sufficient being added to 

 make a good slope. Care must be taken to avoid soiling the 

 other parts of the test tube. The tubed medium is inspissated 

 at 80 C. on two successive days. 



The Detection of Tubercle Bacilli in Butter. The inocula- 

 tion method is the only satisfactory one. The butter is placed 

 in centrifugal tubes which are stood in warm water at 40 0. 

 until the butter is completely melted. The material is centri- 

 fugalised while liquid, and the sediment inoculated into 

 guinea-pigs in the ordinary way. It is difficult to keep the 

 butter liquid during the centrifugalisation. 



II. DETECTION AND ISOLATION OF DIPHTHERIA BACILLI 

 FROM MILK 



This organism has only been found in milk on a very 



1 Kolle und Wasserraann, Htmdbuch, Erganzungsband 1906, p. 133. 



2 Method communicated to the writer by Dr. F. Griffith, and used in the 

 work of the Royal Commission. 



