256 
Arthropods Transmission of Disease 
Knab’s article should serve a valuable end in checking irrespon¬ 
sible theorizing on the subject of insect transmission of disease. 
Nevertheless, the principles which he laid down cannot be applied 
to the cases of accidental carriage of bacterial diseases, or to those 
of direct inoculation of pyogenic organisms, or of blood parasites 
such as the bacillus of anthrax, or of bubonic plague. Accumulated 
evidence has justified the conclusion that certain trypanosomes 
pathogenic to man are harbored by wild mammals, and so form an 
exception. Townsend believes that lizards constitute the natural 
reservoir of verruga; and it seems probable that field mice harbor 
the organism of tsutsugamushi disease. Such instances are likely to 
accumulate as our knowledge of the relation of arthropods to disease 
broadens. 
