266 
known. Fleas, too, need attention. The dreaded 
plague is spread by means of infected rat-fleas 
that leave their natural host and pass to mam 
Fleas also convey other diseases, and apart from 
this, the broken rest due to flea-bites is a factor 
that makes even such an_ insignificant insect 
worthy of consideration. 
Blood-sucking leeches occur in Belgium and 
Germany, and also in parts of India, Ceylon, 
Egypt, and Palestine. These animals, although 
not belonging to the arthropoda, constitute a 

Fic. 2.—Ffphestia kiihniella. Moth-infested biscuit. 
From ‘‘ Lhe Minor Horrors of War.” 
very real pest in some places, as they may occur 
in drinking water. The straining or filtering of 
drinking water and boiling it before use are simple 
means of avoiding distressing throat and lung 
troubles. The existence of voracious Indian land 
leeches, lurking among foliage in wait for their 
prey, will probably be news to many, but pro- 
vides a useful hint with regard to sites for camp- 
ing. 
Man is affected by insect parasites not only 
through direct attacks upon himself, but also by 
infestation of his dwellings and his food. Flies 



Fic. 3.—usca domestica, the house-fly, in the act of 
regurgitating food. x4} (After Gordon Hewitt.) 
From ‘‘ The Minor Horrors of War.” 
and flour moths are therefore discussed. Fortun- 
ately, the occurrence of ‘‘ maggotty’’ biscuit 
(Fig. 2) is not so common as formerly, but the 
possibility of its recurrence under war conditions 
should be remembered. Flies are a more serious 
pest. House-flies are concerned with the convey- 
ance of several diseases to man, typhoid fever 
perhaps being the best known. The typhoid bacilli 
can live for six days in the intestine of a house- 
fly, and food and milk can be polluted by its pro- 
miscuous visits during this period (Fig. 3).  In- 
NO. 2375, VOL. 95] 
NATURE 

[May 6, 1915 
life-history and habits of 
flies is sufficient to cause anyone to join 
in the anti-fly crusade. The love of filth and 
carrion displayed by the various blow-flies or 
meat-flies, too, is a means of spreading disease, 
and there are records, even in the present war, of 
wounded men suffering agony from the presence 
of fly larve in their neglected wounds. The 
abolition of filth is the simplest means of securing 
freedom from flies by destroying their breeding 
places. . 
The relation of insect pests to the health of 
men and animals is a subject of interest to all, 
and it is not surprising that the large first edition 
of Dr. Shipley’s book was practically exhausted in 
a month, and that a second edition is in prepara- 
tion. The combination of literary charm and 
scientific information of practical utility, parti- 
cularly at the present time, is certain to ensure 
its continued success. H. B. Fantuam. 
sight into the 

TE SUPPLY (Oh TORT CAL RAG IEA sss 
Gere serious position in which this country was 
placed at the outbreak of hostilities by the 
almost complete stoppage of the supply of optical 
glass and of the import of optical instruments, 
is at last attracting the attention of the public 
which should have been much sooner focussed 
upon it. The importance of the subject was early 
recognised by the British Science Guild, which 
referred its consideration to its Technical Optics 
Committee. This committee, after fully investi- 
gating the evidence then available, reported, and 
the guild forwarded an important report to the 
Board of Trade; the report was printed in full in 
our issue of March 25 (page 104). So far as can 
be ascertained, however, no official action appears 
to have resulted. 
Quite recently, Sir Philip Magnus, the member 
for the University of London, put on the order 
paper of the House of Commons questions 
addressed to the representatives of the War Office 
and the Admiralty, asking whether the supply of 
optical glass and optical instruments for the use 
of the Services was keeping pace with their im- 
mediate requirements. To these questions official 
replies of the stereotyped order were given and, 
in addition, the representative of the Admiralty 
informed the House that a large firm of makers 
of optical glass in this country ‘“‘had greatly in- 
creased their output and were still adding to their 
plant.” Before these replies were given, a long 
letter on the subject was published in the Times 
over the signature of Dr. Walmsley, the Principal 
of the Northampton Polytechnic Institute, an 
institute which is intimately associated with tech- 
nical instruction in applied optics. There had 
also been other allusions to the matter in the Press. 
In the report of the British Science Guild, 
referred to above, the main points involved are 
clearly indicated; and with regard to the supply 
of optical glass for instruments required by the 
Government, the report states that at the time of 
its issue there seemed to be no call for any special 

