XII] ELEPHANTIASIS 217 



It is evident, therefore, that if this filaria escapes into water, 

 either by the death of its insect host, or some other cause, it is 

 perfectly adapted for the penetration of any skin with which it 

 may come in contact. This was probably the original manner 

 in which the parasite was carried by mosquitoes, and the 

 possibility of the occurrence of such an " indirect " mode of 

 transmission, concurrently with the more recently acquired 

 " direct " method, should not be ignored. 



Pathological effects. In most cases F. bancrofti does not seem 

 to exercise any marked injurious effect on its host; patients 

 often shew filariae in their blood for many years and all the time 

 appear in perfect health. Under certain conditions, however, 

 the adult filaria may give rise to various pathological symptoms, 

 mainly as a result of obstructing lymphatics. Amongst these 

 affections may be mentioned chyluria, lymph scrotum, vari- 

 cose groin glands, etc. In some instances a living worm, or a 

 bundle of worms, may plug the thoracic duct and act as an 

 embolus, or originate a thrombus ; in others, they give rise 

 to inflammatory thickening of the walls, as a result of irritation, 

 and thus lead to obstruction from the consequent stenosis. 

 In such cases the embryos may disappear from the blood, 

 usually as a result of the death of the adults. 



Sometimes adult filariae occur in large numbers in the lym- 

 phatic glands and also in the epididymis, testis and tunica 

 vaginalis. In these situations the worms may die and become 

 cretified, and whether alive or dead they cause fibrosis and 

 blocking of the glands. 



Elephantiasis. Of all the affections that are supposed to 

 be due to filariasis, elephantiasis is the most important, as it 

 occurs in most tropical countries. The disease may be denned 

 as a chronic inflammatory hypertrophy of the fibrous con- 

 nective tissue in some region of the body, induced by lymph 

 stasis and resulting in a considerable hypertrophy of the skin 

 and subcutaneous tissues. It most commonly affects the legs, 

 scrotum, vulva, arms and breast. The resulting growths may 

 become of enormous size, especially in cases of elephantiasis of 

 the scrotum, in which this organ may attain the weight of over 

 230 pounds. According to Manson the condition of lymph 



