ILLUSTRATIONS 



An artificial lake, nearly dry and partly 

 filled with rubbish, has become a breeding- 

 GROUND for dangerous mosquitoes . . Frontispiece 



PAGE 



Fig. i. A lamprey 2 



Fig. 2. Sacculina 2 



Fig. 3. Trichina spiralis 2 



Fig. 4. An external parasite, a bird-louse (Lipeurus 



ferox) ...... 3 



Fig. 5. An internal parasite, a tachina fly {Blephari- 



peza adusta) 3 



Fig. 6. Work of an internal parasite, puss-moth larva 



parasitized by a small ichneumon fly ... 3 



Fig. 7. Typhoid fever bacilli 20 



Fig. 8. Amoeba 20 



Fig. 9. Euglina virdis 21 



Fig. 10. Spirocheta duttoni 21 



Fig. 11. Paramecium 22 



Fig. 12. Vorticella 22 



Fig. 13. Pathogenic protozoa; a group of intestinal 



parasites 22 



Fig. 14. Castor-bean tick {Ixodes ricinus) 28 



Fig. 15. Texas fever tick 28 



Fig. 16. Texas fever tick {Mar gar opus annulatus) ... 29 



Fig. 17. Amblyomma variegatum 29 



Fig. 18. Ornithodoros moubata 36 



Fig. 19. The follicle mite {Demodex folliculorum) ... 36 



Fig. 20. Itch-mite {Sarcoptes scabiei) ........ 37 



Fig. 21. Harvest-mites or "jiggers" 37 



Fig. 22. Horse-fly {Tabanus punctifer) 44 



xi 



