68 ESSAYS ON BACTEEIOLOGY. 



CO very and the importance of its daily use. Some 

 improvements have been made in the methods of ex- 

 amining spiitum which enable us to reach certainty in 

 otherwise doubtful cases. These are, first, liquefac- 

 tion of the sputum by the addition of a small quantity 

 of dilute sodium hydrate. Such liquefied sputum is 

 allowed to settle in a conical vessel, and tbe sediment 

 examined for bacilli by the ordinary means. Second, 

 the addition of liquid carbolic acid precipitates the 

 bacilli-containing masses in the sputum, which may 

 be examined with increased prospect of finding the 

 few bacilli present. Third, the centrifugal machine 

 has been applied for a similar purpose, just as it is ap- 

 plied to secure the rapid deposits of urinary casts. 



I would, in this connection, emphasize the value 

 and simplicity of inoculations upon rabbits or guinea 

 pigs for diagnostic purposes in otherwise obscure 

 cases. 



So far as we can now tell, the tuberculin experi- 

 ment of Koch to arrest tuberculosis has been a failure. 

 We now know more of the reason for expecting such 

 failure than we did when the treatment was promul- 

 gated. However, no one conversant with the prog- 

 ress of bacteriology supposes for a moment that this 

 failure ^\ill, or should, dishearten us or arrest further 

 experiment in this and other diseases. Through the 

 work of Hunter, Cheyne, Klebs and others it has been 

 shown that even Koch himself was ignorant of the 

 substance with which he was dealing, the two former 



