428 THE EVOLUTION OF LIFE. 



lungs, the liver, the heart, the eye, &c., often ending fatally 

 after long-continued suffering. Five other parasites, belong- 

 ing to a different class, are found in the viscera of man the 

 Trichocephalus, the Oxyuris, the Strongylus (two species), 

 the Ancylostomum and the Ascaris; which, beyond that 

 defect of nutrition which they necessarily cause, sometimes 

 induce certain irritations that lead to complete demoraliza- 

 tion. Of another class of entozoa, belonging to the sub- 

 division Trematoda, there are five kinds found in different 

 organs of the human body the liver and gall-duct, the 

 portal vein, the intestine, the bladder, the eye. Then we 

 have the Trichina spiralis, which passes through one phase of 

 its existence imbedded in the muscles and through another 

 phase of its existence in the intestine; and which, by the 

 induced disease Trichinosis, has lately committed such ra- 

 vages in Germany as to cause a panic. To these we must 

 add the Guinea-worm, which in some part of Africa and 

 India makes men miserable by burrowing in their legs; and 

 the more terrible African parasite the Bilharzia, which affects 

 30 per cent, of the natives on the east coast with bleeding of 

 the bladder. From entozoa, let us pass to epizoa. There are 

 two kinds of Acarl, one of them inhabiting the follicles of 

 the skin and the other producing the itch. There are crea- 

 tures that bury themselves beneath the skin and lay their 

 eggs there; and there are three species of lice which infest 

 the surface of the body. Nor is this all. Besides animal 

 parasites there are sundry vegetal parasites, which grow and 

 multiply at our cost. The Sarcina ventriculi inhabits the 

 stomach, and produces gastric disturbance. The Leptothrix 

 buccalis is extremely general in the mouth, and may have 

 something to do with the decay of teeth. And besides these 

 there are microscopic fungi which produce ringworm, porrigo, 

 pityriasis, thrush, &c. Thus the human body is the 



habitat of parasites, internal and external, animal and ve- 

 getal, numbering, if all are set down, between two and three 

 dozen species; sundry of which are peculiar to Man, and 



