418 THE ANIMAL PARASITES OF MAN 



is distinctly transversely striated. The mouth is unarmed. The 

 alimentary canal is straight, the anus opening o'o/ mm. from the tip 

 of the tail. The tail is strongly curved and somewhat flattened on 

 the concave surface. There are three papillae, one large and two 

 small, on each side of the cloaca and one large and two post-anal 

 small papillae. Two curved spicules, <ri66 and 0-08 mm. respectively. 



The adult female is of uncertain length, but much longer than 

 the male, probably about 10 to 12 cm. The head is rounded and 

 truncated ; it measures 0*065 mm. in diameter. The tail is curved. 

 The vulva opens 0-55 mm. from the head. The hand-like cuticular 

 thickenings are well marked. Eggs ovoid with a prolongation at 

 each pole 'Mike an orange wrapped in tissue paper." The larva 

 measures about 300 yu, by 7 p to 8 p ; it has no " sheath." The body 

 tapers from about the last fifth of its length, and terminates in a 

 sharply pointed tail. At about the anterior fifth of the body there 

 is a V spot. 



0. volvulus is found in peculiar subcutaneous tumours, the size of 

 a pea to that of a pigeon's egg. The same patient may present one 

 or several of these tumours. The regions of the body most fre- 

 quently affected are those in which the peripheral lymphatics con- 

 verge. Thus they are usually found in the axilla, in the popliteal 

 space, about the elbow, in the sub-occipital region and in the inter- 

 costal spaces. The tumours are never adherent to the surrounding 

 structures, and can be easily enucleated. They are formed of a dense 

 connective tissue wall and internally a looser fibrous meshwork. 

 This is traversed by a series of canals in which the worms lie, but 

 they are also partly embedded in the denser wall. The canals 

 apparently dilate into Cavities filled with slimy pus-like fluid con- 

 sisting largely of larvae. According to Brumpt the posterior extremity 

 of the male, and the anterior extremity of the female with its vaginal 

 opening, are free in one of the spaces for the purpose of copulation 

 and parturition. If a tumour be cut into and placed in salt solution, 

 Rodenwaldt states that the undamaged males wander out into the 

 solution. 



The formation of the tumours is elucidated by Labadie-Lagrave 

 and Deguy's case. The authors found an immature female Onchocerca 

 volvulus in a lymphatic vessel partly obstructed by an infiltration of 

 fibrin and leucocytes. It appears, therefore, that the presence of the 

 parasites within the lymphatics gives rise to an inflammatory process, 

 and that the consequent fibrinous deposit envelops the parasites, 

 obliterates the lumen of the vessel, and ultimately isolates the affected 

 tract. At any rate, in young tumours the worms appear to lie in 

 a structureless substance permeated by leucocytes in which connective 

 tissue is gradually organized from the periphery, thus isolating the 

 worms. 



