PHYLUM NEMATHELMINTHES 183 



Reproduction and the Life Cycle 



The animals copulate, and at this time the spermatozoa are intro- 

 duced into the vagina of the female to fertilize the mature ova in 

 the oviducts. A mature female may contain as many as 27,000,000 

 eggs. These eggs pass from the host with the feces. Some workers 

 have reported that each female worm in an infected host may pro- 

 duce a crop of eggs in excess of two thousand per gram of feces. 

 Based on this figure, the daily production is computed to be some- 

 thing like 200,000 eggs. These eggs are so resistant that they can 

 be successfully cultured in 1 to 2 per cent formalin, and they may 

 be stored successfully for four years in a refrigerator. The life 

 history is completed only in case the eggs are swallowed by a sus- 

 ceptible host. They hatch in the small intestine of the host and 

 then go on a ten-day journey by way of the blood stream to the 

 liver, thence to the heart, and thence to the lungs. By burrowing 

 out from here, these larvae make their way to the throat, esophagus, 

 and back to the stomach and intestine. After reaching the intestine, 

 the larval worms, 2 to 3 mm. long, grow to maturity in two to two 

 and one-half months. They likely live a little less than a year in 

 the host. 



Relations to Man 



Heavy infestation in man may cause severe hemorrhages and set 

 up pneumonia that is often fatal. Anemia is often the result of 

 such infection; in certain cases the organisms may even tangle in 

 masses and block the intestine until surgical operation is necessary 

 to remove them. The toxic substances from these parasites may 

 bring on coma, convulsions, delirium, nervousness, and other similar 

 symptoms. Drugs like chenopouium, santonin, and hexylresorcinol 

 have been used successfully under physicians' directions as a cure. 

 Effective sanitary disposal of fecal material is the most successful 

 preventive. 



