146 Objects for the Microscope. 



the best to mount for observation. The dots on the head, 

 and the femora being without hairs, distinguish it from the 

 human Flea. 



The eggs of fleas are white, long, and viscid or sticky ; 

 the larvae vermiform, with thirteen segments ; the pupa is 

 enclosed in a silken cocoon. 



PEDICULUS, OR LOUSE, 



a genus of anoplurous insects. 



Man is infested by three kinds of Louse ; but the com- 

 mon head louse is the one usually mounted for observation. 

 It has a flat and nearly transparent body, three pairs of 

 legs, terminated by a claw or hook, and a head which has 

 two simple eyes, and a long sucker concealed in a little 

 fleshy tubercle or snout. They multiply prodigiously, two 

 females producing no less than 10,000 eggs in eight weeks. 

 Leuwenhoek described them minutely, and seems to have 

 watched their manner of feeding and propagating with 

 great interest. Certainly their eggs are curiously formed, 

 with a little moveable lid on a hinge, which opens for the 

 escape of the young larvae, and the egg of the Pheasant- 

 louse is beautifully striated and dotted, giving it the ap- 

 pearance of worked net. Some parts of the internal 

 organization of a Louse are well worthy of attention and 

 dissection ; being naturally transparent, a little soaking in 

 oil of turpentine will dissolve the fat and render many of 

 the organs apparent. 



The nerves of a Louse are remarkable, as forming a thick 

 spinal cord without breaks or intervals, after the ganglia of 

 the head, and from the end of which several rays or nerves 

 are given out to lower parts of the body, a slight constric- 

 tion only marking the united ganglia. These are visible 

 when the insect is properly prepared. The ovaries also are in 

 ten branches of bead-like threads. All the internal apparatus 

 is as perfect as in more beautiful insects, so little reason 

 is there for shrinking from or thinking meanly of even a 

 loathsome louse. 



