72 



Wherein may we distinguish a " true " tubercle from a 

 nodule exhibiting an identical structure ? The question 

 is answered instantly when we consider what constitutes 

 pyaemic pus. Pus is a definite anatomical entity, vary- 

 ing, like tubercle, within certain limits. The pus from 

 a pyaemic joint, may be indistinguishable by the micro- 

 scope from the pus of a simple abscess ; yet there is 

 none the less a vital, or rather a fatal difference. Fresh 

 pus from a simple non-specific abscess does not cause 

 pyaemia, as Virchow long ago proved ; a minute quan- 

 tity of pyaemic pus is fatal through pyaemia, as the death 

 of many a physician has testified. The tubercle from 

 Limburger cheese does not cause tuberculosis, as Schot- 

 telius himself admitted ; the tubercle from tuberculosis 

 never fails to do so, as all observers testify. Pyaemic 

 pus, however similar histologically to that from croton- 

 oil or turpentine, is unerringly distinguished by its infec- 

 tiousness ; tubercles from tuberculosis, though anatomic- 

 ally identical with those from mechanical irritation or 

 from syphilis, contain a something sure to propagate tu- 

 berculosis in the proper soil. The non-specific pus of a 

 simple wound or abscess may acquire pyaemic properties, 

 without the intentional or even conscious introduction of 

 pyaemic matter ; the non-specific cheesy products of a 

 simple inflammation may acquire infectiousness without 

 the intentional introduction of a specific agent. This 

 acquisition of pyaemic infectiousness never occurs, as 

 has long been known, without bacteria ; and the day has 

 come when we can say that the infectious tubercle of 

 tuberculosis is also characterized by a bacterium. 



Perhaps the clearest proof because a demonstration 

 of the infectiousness of tuberculosis is furnished by com- 

 parative observations upon the eye made by Baum- 

 garten, Cohnheim, Salomonsen, Deutschmann, and 

 others. When the piece used for infection is fresh, 

 Cohnheim says " the irritation at the commencement 

 usually soon subsides, the particle becomes gradually 

 smaller, and can indeed entirely disappear, and for some 

 time the eye then appears entirely clear and intact, until 



