INSECT LARVAE 65 



EXERCISE 36b 



HELMINTH OVA 



In studying the characteristics of Helminth eggs the following 

 from Manson's "Tropical Diseases" is suggestive: "The points 

 to.be attended to in the diagnosis of ova are size, shape, color, 

 thickness, roughness, smoothness and markings on the surface of 

 the shell; the presence or otherwise of yolk spheres, of a differ- 

 entiated embryo, or in the case of the cestodes, of the three 

 pairs of embryonic booklets; the existence of an operculum in 

 the case of certain trematodes and of the broad tapeworm 

 (Dibothriocephalus). The ova of the same species of parasites 

 vary but slightly, and are in every instance stable and definite 

 for correct diagnosis." 



With the above in mind, study, describe and draw the following 

 species of ova: 



a. Strongylus ovis pulmonis, the lungworm of sheep. 

 b. Trichocephalus trichuris, the whipworm of man. 



c. Necator americanus, the American hookworm of man. 



d. Ascaris lumbricoides, the roundworm of man and swine. 



e. Fasciola hepatica, the sheep liver fluke. 



f. Schisostomum (Bilharzia) hcematobium, a trematode of 

 humans which produces haematuria. 



g. T&nia s,olium, the pork tapeworm of man. 



I 



EXERCISE 37 



INSECT LARVE 



This exercise is to give the student facility in distinguishing 

 insect larvae from worms, an important matter when it is neces- 

 sary to trace modes of infection and to administer remedial 

 measures. 



