ZOOLOGY FOR MEDICAL STUDENTS 



CHAP. 



male and 45-50 mm. in the female, and it is easily recognized by the fact 

 that the anterior portion of the body forms a fine filament which is threaded 

 through the intestinal lining and serves to anchor the worm in position. 

 The eggs, of an elongated ellipsoidal form and measuring about 52 /* 

 in length by 23 /* in width (Fig. 90, A), pass to the exterior and if the 

 soil is moist go on developing to an advanced embryonic stage. If 

 swallowed at this stage— which may last for a prolonged period — the 

 young worms hatch out in the alimentary canal of their new host and in 



about a month are mature and 

 producing eggs. 



OXYURIS 



0. vermicularis is a small 

 nematode ( i 3-5 mm., ? 10 mm.) 

 which occurs in the large intes- 

 tine of man and is the usual 

 cause of the complaint popularly 

 known as " worms " in children. 

 The female when ready to deposit 

 the eggs travels down the intes- 

 tine towards the anal opening^jii, 

 the eggs are deposited either on 

 the skin or in faecal matter. If 

 swallowed there hatches out from 

 the egg a young worm which de- 

 velops into an adult like the 

 parent. 



Fig. 91. 



Trichocephalus trichium ? x 6. u.c, Alimentary AnCYLOSTOMA 



canal ; g, uterus ; M, mouth. 



The Miner's Worm or Hook- 

 worin {Ancylostoma duodenale) although small in size ((J about lo mm., 

 ? about 12-13 nim.) is yet a very dangerous parasite of man, for it is 

 liable to occur in the small intestine in enormous numbers and cause 

 profound anaemia. It occurs in practically all the warmer parts of the 

 world and is particularly prevalent in Egypt and some parts of India, 

 and in the Southern States of North America. In colder climates it is 

 apt to be introduced and flourish amongst workmen where the necessary 

 conditions of warmth and moisture are present, as in tunnels and rhines. 

 In mining districts its appearance should always be borne in mind as a 

 possible danger. 



