THE HEAD-LOUSE OF MAN. 97 



of the skin in the particular place w^here 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 it is 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 inovement 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. In time 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 w^ere 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 



