152 



TUBERCLE BIOPLASTS. 



Living tubercle germs will not be considered as 

 very closely related to the contagious particles which 

 are the active agents in the propagation of contagious 

 fevers. There is, however, reason to think that 

 particles of living growing tubercle exist sufficiently 

 minute to be supported by the atmosphere and 

 carried long distances ; while there are many facts 

 which are considered by some sufficiently conclusive 

 to justify the opinion that tubercular disease of the 

 lungs is at least in some instances contagious. And 

 it is certain that the most recent observations in 

 connection with the question of the nature and mode 

 of propagation of tubercle, so far from militating 

 against this view, tend rather to support it. That 

 tubercle is not eminently contagious is certain, while 

 the probabilities of minute particles of living growing 

 .tubercle escaping into the air while it remains in the 

 air-cells of the lungs, or rising in a living state into 

 the atmosphere from the sputum after its expectora- 

 tion, are not great. At the same time neither circum- 

 stance can be regarded as impossible, neither view 

 can be held to be untenable. 



The manner in which the bioplasm of tubercle 

 multiplies is represented in Fig. 73, pi. XIX, where it 

 is seen extending round a small artery in the areolar 

 tissue of the external coat. The living particles 

 obstructed in the vessel make their way through its 

 lining membrane and between the fibres of the 

 muscular coat, until they reach the areolar tissue 



