654 



NEMA THELMINTHES 



RemarkSc— This is one of the most common parasites in the tropics. 

 It is, however, possible that other species escape recognition by being 

 casually considered to be Ascans lumhricoides. It is usually met 

 with in the small bowel, but may be found post mortem in the 



Fig. 281. — Development of Ascans lumhricoides. 

 (After Stiles.) 



stomach, oesophagus, mouth, nose, larynx, trachea, or bronchi. It 

 may also be found escaping from the anus. More rarely it has been 

 seen in the liver, causing abscesses, Jin the pancreatic duct, and in 

 the vermiform appendix,'' and in worm^abscesses in the body-wall. 



Usually it gives rise to 

 no symptoms, but at 

 times, when in large 

 numbers, it may cause 

 pathological effects. 



Morphology.— It is yel- 

 lowish in colour, with 

 often a faint trace of a 

 reddish tinge. In form 

 it is spindle-shaped. Male 

 is 15 to 25 centimetres in 

 length and 3 millimetres 

 in diameter. The pos- 

 terior extremity is conical, 

 and bent ventrally, with 

 two spicules 2 millimetres 

 in length, and broader at 

 the tips. On each side 

 of the cloaca there are 

 seventy to seventy-five 

 papillae, of which seven 

 pairs are post-anal. 

 Female is 20 to 40 centimetres 'in flength by 5 millimetres in 

 breadth. The vulva is at the junction of the anterior and middle 

 thirds of the body. 



Life-History "The eggs are laid in the small intestine, and appear 

 unsegmented in the fseces. They measure 50 to 70 ^ in length by 

 40 to 50 in breadth, surrounded by a thick transparent shell, 



Fig. 282. — Ascaris lumhricoides newly 



HATCHED. 



(Microphotograph by J. J. Bell.) 



