634 



NEMA THELMINTHES 



There are two unequal curved retractile spicules. The larger 

 measures o-6 millimetre and the smaller o-2 millimetre in length. 

 They consist of a basal portion, which is broad, rigid, and chiti- 

 nous, measuring 0-17 millimetre in the larger and 0-12 millimetre 

 in the smaher spicule, and a long, thin, colourless, cylindrical, 

 sHghtly undulating terminal portion. 



The female, while more or less transparent, is longer and thicker 

 than the male, and measuring 76 to 100 milhmetres in length, with 

 a thickness of 0-185 millimetre. 



The mouth is situated at the anterior extremity, being 8 /j, in 

 diameter, and leading into an oesophagus which passes insensibly 

 into the intestine. This terminates in the anus, situated 0-28 milli- 

 metre from the incurved posterior end. 



The vulva, situate 1-2 millimetres from the anterior extremity, 

 opens into a single vagina, from which two uterine tubules run 

 along most of the length of the body. These tubules contain the 

 eggs and embryos in various stages of development. 



Cobb's formula is : — 



-0-36, 3-64 (?), 1-22, 99'5 

 -0-145, 0-377 (?), 0-254, 0-147 



The numerator indicates lengths from the anterior extremity to (i) base 

 of oesophagus; (2) nerve ring; (3) posterior pharyngeal constriction; (4) vulva 

 in females or middle in males; (5) anus. The denominator represents trans- 

 verse measurements at the same levels. All measurements are expressed as 

 percentages of the total length. At the present time Cobb's formula is not 

 accepted as a reliable guide to the parasitic species. 



Life-History. — The males and females may be found coiled to- 

 gether in the Ijnnphatics of the scrotum, the arm, the leg, hydro- 

 celes of the cord, epididymis, or testicle, and more rarely in those 

 of the pelvis and abdomen. The males are less numerous than the 

 females. 



When placed in saline solutions, they show active movements, 

 coiling and uncoiling themselves for several hours. 



In the uterus of the female, as has already been stated, eggs may 

 be noted in all stages of development. 



At first nearly round, measuring 50 by 34 ju,, and containing a 

 coiled-up embryo, the eggs become more and more elongated by 

 the movements of the embryo, until in the anterior part of the 

 uterus they are much longer than broad. Finally, they escape 

 through the genital pore, and enter the l3nnph-stream, along which 

 they travel through lymphatic vessels and glands, the thoracic duct, 

 the right side of the heart, and the lungs, to reach the peripheral 

 circulation, where they are best seen at night; hence the name 

 Microfilaria nocturna. In the blood they appear as little wriggling 

 filiform bodies, knocking the corpuscles about, but not moving 

 from the position in which they are lying. The Microfilaria in the 

 blood are said to be a little larger than those in the uterus, which 

 is thought by Penel to be due, not to growth, but to inhibition of 

 fluid by osmosis. 



