THE DIAGNOSIS OF TUBERCULOSIS 131 
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THE DIAGNOSIS OF TUBERCULOSIS 
The laboratory methods of diagnosing tuberculosis consist in 
finding the tubercle bacteria in the suspected material. In the 
living animal, tuberculin can be applied to determine whether 
or not a reaction will occur. With suspected tissues in the 
laboratory the following methods may be used: 
1. Bacteriological methods. 
z. Animal inoculation. 
The methods of staining tubercle bacteria and media for their 
cultivation were described in Exercises XVII and XXVIII. 
Cultivation of tubercle bacteria. To isolate this organism 
from tuberculous lesions and cause it to multiply readily on 
artificial media necessitates a special and very careful pro- 
cedure. When it becomes accustomed to artificial media its 
continued cultivation is not difficult. Dr. Theobald Smith 
of Harvard University (Journal of Experimental Medicine, 
Vol. III. (1898), p.-451) has the credit of formulating a 
method by combining details in such a manner that the pro- 
curing of cultures is, in most cases, possible. Dog serum is 
used. The method, as he gives it, is as follows: 
“The dog was bled under chloroform and the blood drawn 
from a femoral artery, under aseptic conditions, through sterile 
tubes directly into sterile flasks. The serum was drawn from 
the clots with sterile pipettes and either distributed at once 
into tubes or else stored with 0.25 to 0.3% chloroform added. 
Discontinued sterilization was rendered unnecessary. The 
temperature required to produce a sufficiently firm and yet 
not too hard and dry serum is for the dog 75°to 76°C. For 
horse serum it is from 4° to 5° lower. The serum was set in a 
thermostat into which a large dish of water was always placed 
to forestall any abstraction of moisture from the serum. About 
