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THE AMERICAN NATURALIST [Vol. LI 



whereby the germ may be avoided by all susceptible folk. 

 We are warned to avoid the places where the germ lurks, 

 to boil our drinking water and to put cotton in our noses ; 

 and of course this has been of immense value in prevent- 

 ing infection in the case of many communicable diseases. 

 But this conception of escaping the germ, a procedure 

 still by force of habit widely applied, unfortunately does 

 not work out successfully in all cases, simply because we 

 have at last found that the germ is not always escapable. 

 It may be right with us day and night; and whether we 

 succumb to an eventual invasion depends not upon our 

 side-stepping the organism, but upon our maintaining cer- 

 tain of the body defenses at the proper level of efficient 

 working. The case of Trichomonas in its proper host is 

 an instance. For twenty years (under other names) it has 

 been consistently avoided and wholesomely feared by in- 

 telligent turkey raisers. Five hundred regulations more 

 or less have been directed against it; and now we find that 

 it is always there and always will be there. To keep it in 

 an amicable state, to deter it from making destructive 

 excursions into the tissues, all that is required is to main- 

 tain a normal and hygienic condition of the intestinal 

 tract, whatever this may mean ; this alone appears to be 

 sufficient. Thus, although no other intestinal protozoan 

 is able to exert, in a brief time, a greater destructive 

 activity than Trichomonas when properly aroused, still 

 we are far from justified in placing its name upon the 

 blacklist of unqualifiedly pathogenic types which are, by 

 both heredity and training, trouble-makers. On the other 

 hand we can not continue to place this flagellate in that 

 sainthood of parasites, the ''harmless commensals," since, 

 upon occasion, it may be far from harmless. Trichomonas 

 must now be registered as a facultative parasite, which 

 offers a wealth of interesting subject-matter for research 

 covering several fields of biological study. 



