400 NATURAL SCIENCE. May, 1893. 
abnormal activity—which is inflammation—can be supposed to continue for months 
or years. Nor does it seem to me probable that an increased rate of production of 
the leucocytes within the body could be rendered permanent by the temporary 
action of the attenuated virus; for it is to be remembered that the immunity is 
supposed to extend over certain prolonged intervals—nine months in splenic fever, 
according to Pasteur, and seven years for the small-pox, according to the medical 
faculty ; and if protective inoculation merely consists in the increase in the strength 
and activity of the standing army of leucocytes, then one inoculation should suffice 
for all diseases ; he who is protected by inoculation with the cholera virus should be 
proof against small-pox, and the virus of scarlet fever should protect against typhus. 
Moreover, might not such a state of leucocytal activity be produced by other means, 
without the introduction of microbes or poison from a diseased animal—an idea 
which, to say the least, is lacking in poetry? That such were the case is, indeed, 
a ‘‘consummation devoutly to be wished’’ and prayed for. If Dr. Hurst can prove 
his proposition he will have the thanks of a long-suffering public, threatened with 
the nightmare anticipations of a life spent in being inoculated—a veritable flying 
from ‘‘ the ills we have to others that we know not of.” 
Finally, I must remind Dr. Hurst that the inoculation liquids of many experi- 
menters contain no microbes. Dr. Koch’s consumption vaccine, I believe, contained 
none, nor does that of Dr. Kraftkine. 
G. W. Butman. 
‘“TWINS AND TRIPLETS" IN Doris. 
Mr. J. ARTHUR THOMSON refers to the frequency of ‘twins and triplets” in 
Doris, meaning thereby two or more embryos developing within a single egg, and 
suggests that it may be due to “‘ the fact that the ribbons [of eggs] are battered to 
and fro by the surge.” 
I have observed the same phenomenon, however, in eggs laid by a Doris in an 
aquarium, and not exposed to any movement at all. 
April 15, 1893. C. HERBERT Hurst. 
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ERRATA. 
. 254, line 21, for ‘‘ Caprettz”’ read ‘‘ Caprellz.”’ 
. 255, line 13 from bottom, for ‘* Hasting’”’ read ‘‘ Harting.”’ 
. 259, the block was lent by Dr. Sclater. 
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