Cultivation 



665 



tray. The skin is ripped up and turned back. The exposed ab- 

 dominal muscles are now washed with bichlorid solution and a piece 

 of gauze wrung out of the solution temporarily laid on to absorb the 

 excess. With fresh sterile forceps and scissors the abdominal wall 

 is next laid open and fastened back. With fresh sterile instruments 

 the spleen, which should be large and full of tubercles, is drawn 

 forward and, one after another, bits the size of a pea cut or torn off 

 and immediately dropped upon the surface of appropriate culture- 

 media in appropriate tubes. The fragments of tissue from the 

 spleen of the tuberculous guinea-pig are not crushed or comminuted, 

 but are simply laid upon the undisturbed surface of the culture 

 medium and then incubated for several weeks. If no growth is 

 apparent after this period, the bit of 

 tissue is stirred about a little and the 

 tube returned to the incubator, where 

 growth almost immediately begins from 

 bacilli scattered over the surface as the 

 bit of tissue was moved. As the ap- 

 propriate medium, blood-serum was 

 recommended by Koch; glycerin agar- 

 agar, by Roux and Nocard; glycerinized 

 potato, by Nocard; coagulated dogs' 

 blood-serum, by Smith, or coagulated 

 egg, by Dorset, may be mentioned. 

 The most certain results seem to follow 

 the employment of the dogs' serum 

 and egg media. 



Cultivatio n. Blood-serum. Koch 

 first achieved artificial cultivation of the 

 tubercle bacillus upon blood-serum, 

 upon which the bacilli are first appa- 

 rent to the naked eye in about two 

 weeks, in the form of small, dry, 

 whitish flakes, not unlike fragments of 

 chalk. These slowly increase in size at 

 the edges, and gradually form small 



scale-like masses, which under the microscope are found to consist 

 of tangled masses of bacilli, many of which are in a condition of 

 involution. The medium is so ill adapted to the requirements of 

 the tubercle bacillus and gives such uncertain results that it is no 

 longer used. 



Glycerin Agar-agar. In 1887 Nocard and Roux* gave a great 

 impetus to investigations upon tuberculosis by the discovery that 

 the addition of from 4 to 8 per cent, of glycerin to bouillon and agar- 

 agar made them suitable for the development of the bacillus, and 

 that a much more luxuriant development could be obtained upon 

 * "Ann. de PInst. Pasteur," 1887, No. i. 



Fig. 272. Bacillus tuberculo- 

 sis on "glycerin agar-agar." 



