(t. H. F. Nuttall 
95 
In the case of corporis, the nature of the external clothing must 
play an important part in respect to its liability to pick up lice that 
are brought in contact with it. The rougher the surface the better it 
is for lice to cling to. A somewhat similar instance is afforded by 
certain ticks which infest long-haired dogs much more readily than those 
that are smooth-haired. The slightest effort only is required of the 
louse to cling to rough cloth, one might almost say that no effort is needed, 
for dead lice can be readily picked up with a piece of rough cloth, because 
the six long and sharp claws on the feet penetrate among the fibres like 
so many fine curved needles. On the other hand, owing to the structure 
of the louse’s feet, it is incapable of clinging to smooth surfaces, and 
a knowledge of this has led to the very general use of smooth overalls 
(oilskin, rubber) and foot wear for those who are exposed to louse 
infestation. In the laboratory, we often keep the lice we are raising 
in wide-mouthed unstoppered bottles, knowing that they cannot 
escape because they are unable to creep upward on clean glass, and, 
even when it is horizontal they tumble about on it and make no headway. 
When corporis are once established in clothing they are but mode¬ 
rately influenced by its character. Clothing composed of rough woolly 
fabrics, especially where there are numerous folds and seams, affords 
the best protection to them. The use of silk underwear has been much 
advocated as being a protection against lice, on the assumption that it 
affords them a poor foothold and that they are less prone to oviposit 
upon it. There is no doubt, relatively speaking, that silk is not as suited 
to the louse as woollen materials, but it affords no safeguard against 
continued infestation. Lice oviposit upon silk without difficulty 
(see p. 132) and they cling well to silk fabrics, especially tricot. Pinkus 
(1915, p. 24) states that he once saw a lousy rabbi in Warsaw who was 
clothed in silk. 
The main influence in permitting infestation to attain a severe 
character consists in the continuous wearing of clothing. This has been 
brought home to everybody in the present war. In former times, 
when lousiness pervaded all sections of society from king to beggar, 
it was observed that lice “especially trouble persons who cannot change 
their linen or other apparel frequently” ; thus wrote Leeuwenhoek in the 
seventeenth century, at a time when most people ordinarily harboured a 
few lice. The frequent change of apparel was the agency which kept the 
numbers of the vermin down to a normal standard, for the louse popula¬ 
tion, clinging chiefly to the clothing, was removed periodically, thereby 
reducing the number upon the person sufficiently for practical purposes. 
