40 GUIDE TO THE STUDY 



be included. Demonstrations of the larvae in the skin may be 

 purchased. 



CHARACTERISTICS OF THE STRONGYLOIDEA 



Among the most important nematode parasites of man and 

 animals are the blood-sucking hookworms and related forms 

 grouped in the superfamily Strongyloidea. They are of moderate 

 size with an elongate, cylindrical, rarely filiform body. The males 

 possess a caudal bell-shaped inflation known as the bursa which is 

 supported by thickened rays and has two equal or subequal 

 spicules. The oesophagus is more or less swollen posteriorly 

 but never with a terminal bulb. 



We shall study the common dog and cat hookworm, Ancylos- 

 toma caninum, as the most available example of the important 

 hookworms. 



PRACTICAL WORK 



Ancylostoma caninum. — Compare the general form of the 

 hookworm body with that of Ascaris lumbricoides. Note that 

 the anterior end is bent dorsad and that it bears the wide mouth 

 or buccal cavity. On the female locate the vaginal opening 

 somewhat more than two-thirds of the length of the worm 

 caudad, and the anal opening near the caudal end. In the male 

 specimen study the characteristic caudal bursa and its supporting 

 rays. How does the caudal end of the male Ascaris differ from 

 this? 



Selecting the specimen which shows most nearly a front 

 rather than a profile view of the head capsule (Fig. 16), note the 

 pair of strong, three-pronged teeth on the ventral wall of the 

 capsule (remember that the head is bent dorsad and hence these 

 teeth appear at the anterior end of the worm). Near the base 

 of the capsule are the two broad, triangular, latero-ventral 

 pharyngeal plates with their apices projecting into the pharynx. 

 Between them is the dorsal pharyngeal tooth, a narrow elongate 

 structure which appears rod-like in this view. Following the 

 short bulbous pharynx is the elongate, cross-striated oesophageal 

 bulb. The intestine passing from this point to the tip of the 

 body is almost concealed by the coils of the reproductive organs. 

 These in the female are the ovarian and the uterine tubes, the 

 latter discharging the eggs through the vaginal opening in the 

 posterior third of the worm. In the male the long coiled testes 

 lying at the side of the intestine open into a broad sac, the seminal 



