254 CLINICAL BACTERIOLOGY. 



and the spleen is drawn forward with forceps sterilized in the 

 flame, as this organ appears to be involved in greatest degree in 

 this mode of infection. A bit of the spleen containing a tuber- 

 culous nodule is excised with sterilized scissors, the nodule is 

 compressed between two aseptic scalpels or glass slides, in order 

 to set the tubercle-bacilli free, and the material thus obtained is 

 transferred by means of a strong platinum wire to the surface of 

 blood-serum tubes. The whole procedure must be carried out 

 with the utmost celerity and with the most scrupulous cleanliness, 

 for should a foreign microorganism gain entrance into the serum- 

 tube, it will soon overgrow the tubercle-bacilli. For the sake of 

 greater security, several tubes are always treated in the manner 

 described. As the tubes must be kept for a long time in the 

 thermostat at a temperature of 37.5 C. (99.5 F.), they are 

 closed with rubber caps that have been sterilized in mercuric- 

 chlorid solution. After the lapse of fourteen days, if the cul- 

 ture be successful, the first signs of growth are observable in the 

 serum-tubes. In the neighborhood of the expressed material 

 there form gray, dry, small scales, which, with low powers of 

 the microscope, appear to be made up of delicate curved lines. 

 Development then progresses slowly, and after the lapse of from 

 four to six weeks it is possible to continue inoculations from this 

 culture. For further culture blood-serum tubes likewise are 

 used. Also in this second generation growth is first observed 

 distinctly only after the lapse of two weeks. 



Subsequent generations, usually after the fifth or sixth, grow 

 more vigorously and more rapidly; and, particularly when a 

 special thermostat is employed and is saturated with steam, so that 

 the rubber caps can be dispensed with, the entire surface of the 

 serum, after from seven to fourteen days, is found strewn with the 

 characteristic dry scales. From the fifth serum-generation trans- 

 ference to glycerin nutrient media may be readily effected. 



Upon glycerin-agar development is much more abundant than 

 upon blood-serum. The bacilli form upon this a grayish, dry 

 deposit of coarse particles, with the same wavy, slightly raised 

 outline. This coating extends downward, and envelops the 

 "water of condensation present, without, however, rendering it 

 turbid ; and if the culture is kept long enough in the thermostat, 

 the deposit grows even upon the free surface of the test-tube, 

 where no nutrient medium is present, and for a considerable 

 distance upward. 



As a fluid culture-medium veal-bouillon with six per cent, gly- 

 cerin is preferably selected, and this is poured into Erlenmeyer 

 flasks. In inoculating bouillon the dry scales must be intro- 

 duced into the nutrient fluid in such a way that they float upon 

 its surface. The tubercle-bacilli have a strong avidity for 

 oxygen, and they develop luxuriantly only where air has surfi- 



