JLbc Storv? of Bir&-3)eatb. 



By W. Geo. CreswelIv, M.D. Durli., L.R.C.P., F.Z.S. 

 (Continued from page 202). 



TTThe formation of these characteristic nodules of 

 I caseous matter is a process depending on more 

 ^^^ than one factor. In the first place it will be 

 remembered that there is a great tendency on 

 the part of the bacilli to crowd together on the walls 

 of the smallest blood vessels, thereby in places 

 gradually reducing the calibre of these vessels. In 

 addition to this mechanical cause a chemical one steps 

 in. The toxins which are thrown out by the bacilli 

 produce a coagulation of the fibrinogen of the blood 

 while yet in the living vessels, similar to that which is 

 so well known to take place when blood is withdrawn 

 from the body and is placed in contact with non- 

 living structures. So we have as an easily understood 

 result of the combination of these two preliminary 

 factors a condition of thrombosis. That is to say, 

 plugs are formed here and there in the network of the 

 minute arteries and capillaries which completely 

 block them. Then, since there is the pressure derived 

 from the heart's pumping action constantly exerting 

 itself from behind, minute ruptures take place in the 

 walls of the blocked vessels, and small extravasations 

 of blood with its contained bacilli and its more or 

 less disintegrated corpuscles are produced in the 

 surrounding tissues. 



Now it is obvious that these extravasations, being 

 now of the nature of dead foreign bodies intruded 



