636 THE MICROSCOPE. 



from this, found upon the body of the very poor and dirtft 

 known as the body or crab-louse. Leeuwenhoek carried his 

 researches on the habits of these insects further than most 

 investigators, even allowing his zeal to overcome his disgust 

 for such creatures as the louse. In describing its mode of 

 taking food, &c., he observes : " In my experiments, 

 although I had at one time several on my hand drawing 

 blood, yet I very rarely felt any pain from their punctures ; 

 which is not to be wondered at, when we consider the 

 excessive slenderness of the piercer ; for, upon comparing 

 this with a hair taken from the back of my hand, I judged, 

 from the most accurate computation I could form by the 

 microscope, that the hair was 700 times larger than this 

 incredibly slender piercer, which consequently by its 

 punctures must excite little or no pain, unless it happens 

 to touch a nerve. Hence I have been induced to think 

 that the pain or uneasiness those persons suffer who are 

 infested by these creatures, is not so much produced from 

 the piercer as from a real sting, which the male louse 

 carries in the hinder part of his body, and uses as a 

 weapon of defence." He found, from experiments made 

 to ascertain the possible increase of these pests, that from 

 two females he obtained in eight weeks the almost in- 

 credible number of 10,000 eggs. 



The Itch-insect, Sarcoptes scaliei (fig. 290, No. 3, 

 magnified 350 diameters). Dr. Bononio was among the 

 first to detect the parasitic character of the disease 

 known as the itch. On turning out one of the pustules, 

 or little bladders, from between the fingers, with the 

 points of very fine needles, tinder the microscope, a 

 minute animal was discovered, very nimble in its motion, 

 covered with short hairs, having a short head, a pair of 

 strong mandibles or cutting jaws, and eight legs, ter- 

 minating in remarkable sucker-like appendages. 



It has no eyes ; and when disturbed it quickly draws 

 in its head and feet, and then somewhat resembles the 

 tortoise in appearance ; its march is precisely that of the 

 tortoise. It usually lays sixteen eggs, which are care- 

 fully deposited in the furrows of the skin in pairs, and 

 hatched in about ten days. It is an air-breathing 

 insect, and to find it carefully search around the skin 



