220 EVOLUTION AND DISEASE 
the spot, and reinforce their comrades ; as a result of 
this encounter many of the leucocytes die, others fuse 
together and form giant-cells : the dead leucocytes form 
pus cells and give rise to the caseous centre in the 
nodules, whilst along its confines, in the bacilliferous 
zone, the conflict continues to rage. The giant-cells are © 
powerful antagonists, for I have seen one contain as — 
many as fifty bacilli. From these nodules the bacilli are — 
conveyed by blood-vessels, or even carried away by the ~ 
leucocytes, and initiate new struggles in distant parts. 
It must also be remembered that after their introduction ~ 
into the body the bacilli will,if the conditions of the host — 
be favourable, multiply very rapidly, and in due course : 
overrun the whole system; nodules arise in the liver, 
lungs, brain, and skin; function is interfered with and 
death results. In addition to the local troubles the 
invasion of an organism by bacteria produces general — 
disturbances, one of the most important being an 
increase of the temperature of the body, usually termed 
fever. 
It must be borne in mind that local lesions are not 
necessary results of the entrance of pathogenic organisms 
into the system. In such a disease as anthrax we have 
one local sore indicating the seat of inoculation, but 
beyond the presence of the bacilli in the blood we have 
no special tissue-change enabling us to identify the 
nature of the disease, the general disturbance and fever 
in anthrax conforming to that characteristic of acute, 
specific, contagious maladies in general. 
The behaviour of leucocytes to pathogenic bacteria 
constitutes the essence of the inflammatory process. It 
