Ope) EVOLUTION AND DISEASE. 
of the specific bacteria ; some are more virulent, others 
are slower in attaining maturity, or are more irritating 
to the tissues. 
This view of the nature of inflammation is of some 
importance, for it shows that the process may take place 
in any compound cellular organism, and it certainly takes 
place in plants ; for example, the galls on leaves due ; 
to the deposition of eggs in their interstices by insects ; 
each insect producing in this way a different variety of — 
gall, so that one leaf may present at the same time 
several varieties of galls. v 
The modification of the inflammatory process accord- 
ing to the nature of the irritant is of interest in its 
bearing on the evolution of specific diseases. The course © 
of a specific contagious disease, whether due to bacterial | 
infection or to noxious agents produced by bacteria, pre-_ 
sents well-marked stages. The first is known as the 
incubation stage, which may vary from a few hours to — 
days, or even weeks: this is succeeded by a stage of 
eruption, in which the body presents manifestations of 
the presence of noxious particles, such as a rash in small- | 
pox, scarlet fever, measles, and the like, or a sore limited 
to a small area of the body, as in glanders, anthrax, © 
syphilis, &c. 
These outward signs are accompanied by fever and © 
general disturbance, marking the maturation of the — 
poison in the organism. After a variable period the signs | 
gradually subside, or terminate the life of the individual, 
or the bacteria continuing to thrive in the organism may, 
with the maturation of successive generations, produce 
periodical disturbance at intervals of several hours, or 
