66 



LECTURE VI. 



The Strongylus gigas is not confined to the human 

 subject, but more frequently infests the kidney of the 

 dog, wolf, otter, racoon, glutton, horse, and ox. It 

 is generally of a dark blood-colour, which seems to be 

 owing to the nature of its food, which is derived from 

 the vessels of the kidney, as, where suppuration has 

 hi W\] taken place, the worm has been found of a whitish hue. 

 The round-worm (^Ascaris lumhricoides Linn.) 

 {Jig. 31.) is perhaps the most anciently known * and 

 common of the human Entozoa, and is that which has 

 been subjected to the most repeated, minute, and suc- 

 cessful anatomical examinations. It is found in the 

 intestines of man, the hog, and the ox. In the human 

 subject the round worms are much more common in 

 children than in adults, and are extremely rare in aged 

 persons. They are most obnoxious to individuals of 

 the lymphatic temperament, and such as use gross and 

 indigestible food, or who inhabit low and damp loca- 

 lities. They generally occur in the small intestines. 



The body is round, elastic, with a smooth shining 

 surface, of a whitish or yellowish colour ; attenuated 

 towards both extremities, but chiefly towards the an- 

 terior one {fig- 31, «), which commences abruptly by 

 three tubercles, which surround the mouth, and cha- 

 racterise the genus. The posterior extremity {d) 

 terminates in an obtuse end, at the apex of which a 

 small black point may frequently be observed. In the 

 female this extremity is straighter and thicker than in 

 the male, in which it is terminated more acutely and 

 abruptly and is curved towards the ventral side of the 

 body. The anus is situated in both sexes close to the 

 extremity of the tail, in form like a transverse fissure. 

 In the female the body generally presents a constriction 

 at the junction of the anterior with the middle third, 

 in which the vulva (e) is situated. 



The body of the Ascaris lumhricoides is transversely 

 ^*'^*Naf "ize!^^^" furrowcd with numerous very fine striae, and is marked 

 v/ith four longitudinal equidistant lines extending from 

 the head to the tail. These lines are independent of the exterior 

 envelope, which simply covers them ; two are lateral, and are larger 

 than the others, which are dorsal and ventral. The lateral lines 



* It is the eAfiivs arpoyyvAoi of Hippocrates. 



