212 bacteriology. 



Preparation of Cultures from Tissues. — 

 Under strictest antiseptic precautions, remove from 

 tlie animal the tubercular tissue — the liver, spleen, or 

 a lymphatic gland being preferable. Place tlie tissue in 

 a sterilized Petri dish and dissect out with sterilized 

 scissors and forceps the small tubercular nodules. Place 

 each nodule upon the surface of the blood-serum, one 

 nodule in each tube, and with a heavy, sterilized, looped 

 platinum needle or spatula, rub it carefully over the sur- 

 face of the blood-serum. It is best to dissect away twenty 

 to thirty such tubercles and treat each in the same way. 

 Some of the tubes will remain sterile, others may be 

 contaminated by outside organisms during the manipu- 

 lation, while a few may give the result desired — a 

 growth of the bacilli themselves. 



After inoculating the tubes they should be carefully 

 sealed up to prevent evaporation and consequent dry- 

 ing. This is best done by burning off the superfluous 

 overhanging cotton plug in the gas-flame, and then im- 

 pregnating the upper layers of the cotton with either 

 sealing-wax or paraffin of a high melting-point. This 

 precaution is necessary because of the slow growth of 

 the organism. Under the most favorable conditions 

 tubercle bacilli directly from the animal body show 

 no evidence of growth for about twelve days after 

 inoculation upon blood-serum, and, as they must be 

 retained during this time at the body temperature — 

 37.5° C. — evaporation would take place very rapidly 

 and the medium become too dry for their development. 



If these primary efforts result in the appearance of a 

 culture of the bacilli, further cultivations may be made 

 by taking up a bit of the colony, preferably a moderately 

 large quantity, and transferring it to fresh serumj and 



