104 
ORGANIC DEPENDENCE AND DISEASE 
that in liost-sliells which have been well riddled by these 
tubes and where the channels are closely crowded together 
in numbers, there is very rarely any evidence that one 
crosses another or even touches its neighbors. 
THE DISTINCTION BETWEEN PROTOZOAN AND 
METAZOAN PARASITISM 
Fig. 104. Tlie Silurian scorpioid crustacean 
Eurypterus fischeri from Rootzikull, Russia, 
showing an overgrowth of agglomerated 
tubules which seem to have spread from 
joint to joint but clear all articulating sur- 
faces; a symbiotic and perhaps parasitic 
growth whose nature is not fully under- 
stood. 
Modern epidemiology 
and germ pathology 
which are founded on the 
recognition of the play 
of the protozoan or pro- 
topliytic parasite in dis- 
turbing the health of hu- 
man beings, have at times 
indulged in too hasty ex- 
pression as to the prev- 
alence of protoplastic 
germ disease throughout 
the history of life on 
the earth. Germ infec- 
tion, in the sense of pro- 
toplastic protozoan and 
pro t opliy tic ad j u s tme n t , 
is universal ; it enters 
into every phase of life 
and into every individual 
of the animal and plant 
world. That is, all life 
from highest to lowest is 
shot through with condi- 
tions of disorder result- 
ing from such parasitic 
adjustments. There is no 
exception. The picture 
