476 Worms in the Intestinal Tract. 



pore is at the boundary between the tirst and second third, situated in a ring- 

 shaped depression. Membrane of ovum wavy, ova 66 /x long. Lives in tlie intes- 

 tinal tract of swine and man. 



5. Ascaris marginata, the head of the white or pale reddish body is provided on 

 each side with one oval wing; this makes the worm look somewhat like a lancet; 

 male 5 to 10 cm. long; on the bent posterior portion two narrow wings; female 9 

 to 12 cm. long, posterior end conical; the genital pore in the neighborhood of the 

 first quarter. Ova globular, diameter 75 to 80 fi, membrane wavy (fig. 56). This 

 worm occurs in the small intestine of the dog. (Galli-Yalerio, in 162 dogs dissected 

 in Mailand, found ascarices in 18.5%.) 



6. Ascaris mystax is so much like the preceding one that they are now held 

 to be one and the same species; it is, however, considerably smaller than the Asc. 

 marginata (4 to 6 or 4 to 10 cm. long; 1 to 1.5 mm. wide). It lives in the small 

 intestine of the cat. (Galli-Valerio found this Ascaris in 8 out of 12 cats dissected in 

 Milano.) 



The development of Ascaridae has been demonstrated ]iy the ob- 

 servations of Grassi, Lntz, Einstein, Jammes & JMartin and A. Albrecht. 

 In order that an embryo in the ova, voided by the female in the intes- 

 tinal tract of the host, may develop, sufficient access of oxygen is nec- 

 essary. Hence the development of the embryos can occur only outside 

 of the animal body. "When temperature and moisture are sufficient, 

 wlien free oxygen is accessible and when the reaction of the surrounding 

 medium is acid (Jammes & Martin), then rapid segmentation of the 

 ovum occurs and it terminates in the formation of 

 a lively motile embryo. At a temperature of 37 °C., 

 embryos in the ova of Asc. megalocephala (Al- 

 brecht) are hatched after 3 to 4 days, at room tem- 

 perature only after 24 to 30 days; in ova of Asc. 

 vituli, embryos are hatched after 18 days if the 

 temperature is near that of the animal liody. The 

 development goes on favorably in moderately moist 

 environment, it is prolonged in water, and the 

 latter may bring about partial solution of the yolk. 

 Fig. 56. Ovum of Asca- Light has a retarding influence in the beginning 

 ris marginata. stage of development. Ova which already contain 



embryos appear to be endowed with a particular 

 power of resistance since they retain their viability for 6 months while 

 kept in desiccated horse manure (Albrecht). Unsegmented ova like- 

 wise retain their vialnlity under conditions of cold, however, no seg- 

 mentation occurs at such low temperatures. The liberation of tlie em- 

 bryo never occurs in the external world, only in the alkaline intestinal 

 juice. 



The final development of the worms goes on rapidly after the 

 embryos are once in the intestinal tract; 10 to 12 weeks after arti- 

 ficial infection, ova of ascaris may be found in the feces. Some 

 species of ascaris develop even more rapidly, and fully developed 

 worms of this genius have been found in young dogs, two weeks old 

 (Penberthy) ; Gasteiger has seen clinical signs of roundworm infection 

 in calves 3 weeks old and occasionally in these animals at the age of 

 10 days. 



Natural infection occurs through the ingestion of food or 

 water contaminated with ova, with embryos, or by licking ob- 

 jects wiiere ova have l)een deposited. Ova voided with feces 

 collect on the bedding straw, near watering places, on pastures. 



