ANKYLOSTOMIASIS— UNCINARIASIS 



561 



thickness. The parasite tapers toward the anterior extremity. The intestinal 

 tract begins with a wide slanting mouth, turned toward the back and having 

 six papillae ; it has a bell-like mouth capsule, upon the border of which are six 

 tooth-like chitin ridges. The posterior end of the body of the female termi- 

 nates in a short ten-pin-like point ; that of the male is somewhat bent, termi- 

 nating in a broad umbrella-like ribbed bursa copulatrix, upon which frequently 

 two long spicula of about 2 mm. in length protrude. The bursa copulatrix 

 serves, on account of its contractile parenchyma ribs, as an apparatus, by 

 means of which the males attach themselves to the body of the female during 

 copulation. The female sexual opening is close behind the middle of the body, 

 and is continued as a short vagina. The parts next to the vagina contain the 

 impregnated ova. These have an oval shape and a smooth surface. Their 

 length is 0.063 and their thickness from 0.036-0.04 mm. They are present 

 in enormous numbers in the human dejecta and, according to the time in 

 which they have remained in the intestinal canal, 2 or 

 4^8 segmentation globules may be recognized. Further 

 development occurs only outside of the human organism. 

 For this development the ova require a temperature of 

 from 25° to 30° C, moderate moisture, and a surface 

 distribution. Under these circum- 

 stances, after three to four days at 

 the latest the embryo may be recog- 

 nized. After twenty-four to forty- 

 eight hours more, it finds its way 

 through the pole of the ova, and 

 shows active movements. 



Fig. 54. — Anktlosto- 

 ma. duodbnale : o, 

 male; 6, female. 



Fig. 55. — Ova of the Anktlostoma. 

 duodenale in various stages op 

 Development. 



Fig. 56. — Larva op 

 Ankylostoma Duo- 



DENAliE. 



The young larva is 0.2-0.25 mm. in length and 0.015-0.017 mm. in thick- 

 ness. The posterior end of the body gradually tapers anteriorly to a pouch- 

 like point. The short and narrow opening of the mouth, the spindle-shaped 

 pharynx, and the globular stomach may be distinctly recognized; in the latter 

 a Y-shaped figure, composed of the three pharyngeal teeth, is found in active 

 movement. The intestine terminates in a fine tube, the anus. The embryo 

 soon begins to grow, and after having attained a length of 0.7-0.8 mm. it 

 encapsulates itself. The larva finally lies in a transparent sheath which uni- 

 formly surrounds it. The sheath protects the embryo from external damage, 

 so that for months in this encysted state it may retain its power of further 

 development. Introduced into the human intestine, after dissolution of its 

 chitin capsule in the small intestine, the parasite develops to maturity, iive 

 37 



