ON SEWAGE AND PARASITES. 
495 
matter of any kind. All sorts of reagents speedily killed 
the larvae. Mere discoloration by carmine solution, or by a 
drop of permanganate of potash, in the form known as 
Condy's fluid, instantly caused them to assume grotesque 
and unnatural shapes — death sooner or later following from 
the disintegration and resolution of their bodies into minute 
sarcode masses. Still more rapidly poisonous effects were 
produced by the addition of a little sherry or alcohol, though 
the strength of the latter was not more than one part of proof 
spirit to fifty of water. I will only further add that the de- 
velopment of the larvae was equally w T ell accomplished in 
distilled water, and likewise, also, in brackish and sea-water. 
It may be said, indeed, that the addition of salt water revived 
the ciliated embryos when they were on the point of expiring 
in any non-saline medium. 
As regards Bilharzia , therefore, the above data, now pub- 
licly brought forward for the first time, undoubtedly appear 
to favour the notion that little harm can result from sewage 
distribution — so far, at least, as parasitism is concerned. For 
the sake of those who will, perhaps, have derived some com- 
fort in this matter, I am sorry, therefore, to be obliged to 
add that our experiences with the eggs and larvae of other 
parasites placed under similar conditions give results which 
are in many respects precisely the opposite of those just re- 
corded. For lack of time I cannot possibly do justice to 
this view of the case, but must content myself by offering 
the following fragmentary data : — 
Ascarides . — The eggs of the common round worm, Ascaris 
lumbricoides , have been kept alive by Dr. Davaine for a period 
of more than five years. I have myself watched their de- 
velopment in fresh water through all the stages of yelk-seg- 
mentation up to the stage of an imperfectly organized, coiled, 
intra-chorionai embryo, and have kept them in the latter 
condition for a period of three months. Davaine adminis- 
tered some of his five-year-old embryos to rats, and had the 
satisfaction of finding a few of these eggs in the rodents 5 
faeces, with their embryo still living, but striving to emerge. 
He also gave eggs to a cow, and introduced others into the 
stomachs of dogs in small linen-covered flasks. As a 
general result, it may be said that the embryos escaped 
their shells, but those eggs in which the yelk-segmentation 
had not arrived at the early embryonal stage remained un- 
digested. 
So far back as 1853, Yerloren reared coiled intra-chorionai 
embryos in the eggs of Ascaris marginata within a period of 
fifteen days, in distilled water. I have also reared the em- 
