354 ENTOZOA IN RELATION TO PUBLIC HEALTH, ETC. 
contaminations are apt to give rise to dysentery, cholera, and 
fever. Speaking as a helminthologist, I contend that no 
closet-made reports, however valuable from a literary point 
of view, can be of any real practical service unless based 
upon an extensive acquaintance with the various forms of 
entozoa, and also upon evidence as to their prevalence, not 
only in the human subject, but also in the more important of 
our domesticated animals. Even an examination of dead 
animals not ordinarily used as food has indirectly thrown 
considerable light upon questions of general interest in this 
connection. 
In the next place, I may here remark that not only are 
many forms of helminthiasis amongst mankind and animals 
ascribed to particular parasites which are in no way con- 
cerned with their production, but a still larger number of 
diseases have been ascribed as helminthic where neither en- 
tozoon nor parasite of any sort existed. My experiences on 
this head, both professional and otherwise, have been very 
remarkable, and not unfrequently of a painfully interesting 
character. If it be asked, therefore, what good result could 
follow further research in the direction I have indicated, I 
can confidently appeal to the knowledge of entozootics 
already acquired from helminthological investigation ; and I 
am in a position to say that the mere registration of the re- 
lative abundance of different species of entozoa in separate 
“hosts” and localities might alone afford a fair and useful 
criterion as to the extent to which particular entozootics 
normally or abnormally abounded. I have indeed already 
attempted something in this direction, but the labour and 
expense involved in inquiries of this description have pre- 
vented my carrying out the researches to the necessary 
extent. Thus between the years 1857-60 inclusive, I was 
enabled, through the kindness of the authorities of the 
Zoological Society, to examine the bodies of no less than 
122 vertebrates which had died at the menagerie, Regent’s 
Park. Of these animal ee hosts,” I found thirty-eight har- 
bouring, collectively, fifty-one different species of entozoa, 
amongst which was the remarkable Bilharzia haematobia , up 
to that time only known to infest the human body. The 
interest and importance of this fact will be inferred from 
what appears in the sequel. Again, at a subsequent period, 
and with a still more obviously practical end in view, I care- 
fully examined the 620 preparations of entozoa and entozoal 
disease which, by patient searching for many w’eeks, I found 
dispersed throughout nine of the pathological museums of 
the metropolis. The results of this separate investigation 
