l6oO 



THE FILARIASES 



The adult Filaria has been found in the tissues removed by 

 operation from a case of elephantiasis of the scrotum; and, further, 

 the condition of elephantiasis is produced as a rule by a series of 

 attacks of lymphangitis, which in every particular resemble un- 

 doubted filarial lymphangitis. 



It is true that a secondary bacterial infection may possibly assist 

 the development of the disease, for a diplococcus has been found by 

 Dufogere, which he calls the ' lymphococcus,' and his findings have 

 been confirmed by Foulerton. Le Dantec describes a similar 

 organism, which he calls the ' dermatococcus but the main cause 

 of elephantiasis in the tropics is Filaria bancrojti, though it is quite 

 possible that, exceptionally, other causes may lead to occlusion of 

 lymphatics and the formation of elephantiasis. 



Pathology. — -If the parent -worms live in positions in which they 

 do not obstruct the flow of the lymph, and if they are not acci- 

 dentally injured, no pathological effects will be produced on the 

 host; and our observations support Hanson's theory that the 

 presence of the worms may produce no ill-effect upon the host, 

 for we know of a case where for years they have produced no 

 symptoms. 



But if the parent -worms obstruct the circulation of the lymph 

 mechanically — for example, when three or four come together in 

 an important main tymphatic trunk — then the retained lymph is 

 certain by mechanical pressure to damage the tributary channels. 

 Further, if any accidental injury is inflicted upon the female parent- 

 worm, this may cause abortion, and as a result the production of 

 oval eggs instead of elongated embryos (Fig. 268), and these, as 

 will be explained below, are liable to block up the small lymph 

 channels of the skin or of a lymphatic gland. Therefore Low is 

 quite correct in his statement that ' the Filaria is not entirely 

 compatible with health,' for very slight causes will produce disease. 



In certain districts from 5 to 27 per cent, of the population is 

 infected with filariasis, and therefore if there are many mosquitoes 

 capable of carrying the worm, there ought to be multiple infection 

 of the individual host ; and one would also assume that the heavier 

 the infection, the greater the liability to obvious disease. Multiple 

 infection would be more liable to occur in natives than in Europeans. 

 As a matter of fact, heavy infections with the parent -worms have 

 not yet been described, though it must be admitted that but few 

 post-mortem examinations are on record; and, moreover, as Fiille- 

 born has shown, it is at times by no means easy, even with the 

 utmost care, to find the adult worms, though they may be found 

 even in fair numbers after considerable search in those parts of the 

 lymphatic system which appear to be least affected. When the 

 case is one of varicose lymphatics, or lymphatic glands with clear 

 lymph, the obstruction must be looked for below the junction of 

 the lacteals with the receptaculum chyli, but when the fluid is 

 milky, it is obvious that the obstruction must be beyond this point. 



The cause of the obstruction may be a coiled-up mass of worms — 



