XVll 



Wound, if the wound heals rapidly no tubercular process may 

 result, the tubercular bacilli, as we have said, being destroyed by 

 llie cells." In a paper which I read at one of the Society's 

 meetings some months ago, I alluded to Menclniikoff's discoveries 

 in connection with the part played by the phagocytes, the white 

 corpuscles of the blood, in the destruction of bacilli. I will now 

 quote Woodhead on the same subject ; for here he refers to those 

 cases Avliere tubercle bacilli and- other pathogenic organisms have 

 already effected an entrance into the human body — "It has been 

 observed," he says, "that a process of localisation occurs even 

 when large caseous patches have been formed, and it has been 

 found that around these patches, just as around an abscess, 

 there is always erected a kind of barrier, made up of vigorous 

 connective tissue cells, small, round, and larger epithelioid 

 cells ; the blood vessels in this cellular zone being comparatively 

 numerous and of considerable size. We have, in fact, in this 

 arrangement of the blood vessels and cells, a making of roads (the 

 blood vessels) for the bringing up and massing of forces (the active 

 cells) around the enemies' camp (the tubercular or caseous mass 

 with the contained bacilli or spores), and by a process of close 

 siege preventing the organisms from making their way outwards, 

 and confining them entirely to their own territory, so that, when 

 they have utilised what food material there is in the degenerated 

 cells, they are no longer able to exist as vegetative bacteria, and 

 only the spores remain — which may, however, remain latent for 

 a long period awaiting a favourable opportunity for another attack 

 on weakened tissues. These spores or hibernating germs are 

 confined within the same area, and the de-ln-b with its contained 

 spores is gradually encroached upon by the surrounding tissues 

 until, eventually, if the mass is not large it may be entirely 

 absorbed, though, owing to the amount of fibrous tissue that is 

 formed by the attacking cells after their activity is somewhat 

 diminished, this process of absorption sometimes goes on very 

 slowly." 



Dr. Koch's tuberculin treatment was suggested by the dis- 

 covery made in the course of a long series of investigations that 

 the bacilli of tuberculosis are not the direct agents by which the 

 tissues are destroyed. They have the power of generating a 

 poison which, if produced in sufficient quantity, weakens and 



