THE HEAD-LOUSE OF MAN. 97 
of the skin in the particular place where the animal is suck- 
ing, whereby access to the capillary system is secured at any 
part of the body. It is apparent, from the whole sttucture 
of the instrument, that itis by no means calculated for be- 
ing used as a sting, but is rather to be compared to a deli- 
cate elastic probe, in the use of which the terminal lobes 
probably serve as feelers. As soon as the capillary system is 
reached, the blood will at once flow in the narrow tube, 
after which the current is continued with increasing rapidity 
by means of the pulsation of the pumping ventricle and the 
powerful peristaltic movement of the digestive tube.”’ 
All true lice have very similar habits, all are blood- 
suckers, but each species inhabits only a certain kind of ani- 
mal, some are even restricted to certain parts of the skin. 
Some animals harbor several species, and five kinds are 
stated to be found upon man, three of which are common 
enough under certain conditions. 
Whenever lice become very abundant by negligence they 
cause great irritation to the skin of their host. Animals 
thus invaded try to overcome this constant itching by rub- 
bing themselving against fences, trees, and buildings, and 
soon wear off their hair and injure their skins. Intime lousy ~ 
animals become weak and otherwise diseased. 
THE HEAD-LOUSE OF MAN. 
(Pediculus capitis De Geer). 
This kind is probably the best known of all species, and 
but few young children in our public schools have had no op- 
portunity to observe their actions. Of course the presence of 
such parasites is an indication, nay, a proof, that personal 
cleanliness is sadly neglected. The old belief that these para- 
sites were indications of healthy blood is not true, and it 
should surely be no longer fashionable to be thus tenanted, 
as it used to be in old times and in some countries. This 
parasite is confined to the human head, and only in extreme 
cases does it spread over the whole body. 
All races of man are infested, and Kuechenmeister reports 
that he even found the eggs of this species in the hairs of a 
