166 TUBERCULOSIS 
It is important to differentiate tubercle bacteria from other acid 
fast organisms that may be present in the saliva, excreta or milk. 
When but one or at most but a few acid fast bacteria are present in 
microscopic preparations from any of these substances, it is necessary 
to establish the identity of the organism. For this certain micro- 
chemical procedures, such as decolorization with acidulated alcohol, 
are recommended. It is safer, however, to resort to guinea pig 
inoculation. Formerly the finding of acid fast bacteria in the excreta 
was considered conclusive evidence of tuberculous infection. Now, 
the large number of saprophytic acid fast bacteria that are known to 
exist and which may readily be found in saliva, excreta and milk 
necessitate careful differentiation of these organisms before a positive 
diagnosis can be made. 
There are two other recognized methods for securing material from 
the lungs for examination for tubercle bacteria. 
Trachea method. This method was introduced by Scharr and 
Opalka* who emphasized the importance of securing mucus from the 
lower part of the trachea and upper bronchi. The method of proce- 
‘dure, briefly stated, is as follows: Render the field of operation over 
the trachea surgically clean. A short incision is made following the 
median Jine down upon the trachea at a place located about level 
with the point of the shoulder. A small sharp tracheal tube is inserted 
between two of the cartilaginous rings. Through this tube is passed 
a long wire in which is an eye armed with a small piece of sterile 
gauze. The wire with the gauze is passed well down the trachea 
where it usually induces a cough. After swabbing out the trachea the 
gauze is withdrawn and placed in a sterile retainer until examined. 
Smears may be made for direct microscopic examination but the most 
successful procedure is to inoculate guinea pigs. This can be done 
by agitating the gauze in a small quantity of bouillon or sterile normal 
salt solution and injecting the washings hypodermically. 
Esophagus method. This requires a small thick-walled cup attached 
to the end of a curved wire. The head of the cow is elevated and the 
cup is passed directly into the esophagus. The cup is withdrawn and 
its contents placed in a sterile retainer. It is examined microscopi- 
cally and by guinea pig inoculations. 
Udall and Birch adopted the esophageal method after testing both. 
They found by this method in the examination of four reacting herds 
*Their report was translated by Dr. A. T. Peters and published in Bulletin No. 5, 
State Board of Livestock Commissioners of IIl., 1912. 
