206 ZOOLOGY FOR MEDICAL STUDENTS CHAP. 



..mi becoming shorter and somewhat sausage-like. Here 

 it runains tor some time, growing to a length of about 1-6 mm., and 



its way to tlit- proboscis. 



Although in many cases no ill effects upon the health of the host 



:>aivnt as a result ol" infection with Filaria bancrofti it is believed 



that this parasite is really the cause of those swellings of the lower parts 



of the body known in medicine as Elephantiasis arabum. This disease 



'losrly in its geographical distribution with Filaria bancrofti: 



its diri-ct cause appears to be obstruction of the flow of lymph and it is 



believed that this obstruction is due to the presence of the filaria. As 



Is the precise method by which the obstruction is brought about 



it is helie\ ed by some to be due to inflammatory change in the lining 



of tin- hmph-spaces, brought on by the presence of the parasite, while 



by others it is attributed to actual blocking of the lymph stream either 



:ps ii' adult parasites or by their eggs. In exceptional cases the 



lemale lays eggs ol" which the shells have not become soft and extensible 



as happens normally, but have on the contrary remained hard and rigid. 



Whereas the natural slender larva in its soft membranous sheath readily 



through the narrow chinks of the lymphatic glands such 



abnormal i-ggs retaining their ellipsoidal form are liable, on account of 



their much greater diameter, to stick in the lymphatic gland and thus 



obstruct the lymph-flow (Manson). 



FILARIA LOA 



Tin's parasite occurs in tropical West Africa (also Uganda), living 



lily in the connective tissue under the skin, in which it creeps 



activi-ly about. Sometimes it attracts particular attention by traversing 



:it of the eye-ball. The adult female measures about 45-60 mm. 



h. the male about 25-30 mm. The young are born in a sheath 



by the softened egg-shell, as in the case of F. bancrofti, and they 



1 their way by lymph channels into the blood. They are about 



the young of F. bancrofti (about 250-300 fj, in length) 



but may be distinguished by their shorter sheath and by the less regular 



' the body. They are also at once distinguishable by their 



for they migrate to the superficial vessels of the skin during the 



uliirh account they were formerly usually known under the 



while the young of F. bancrofti were known as F. noc- 



diffcrence in habit is due to the fact that the transmitting 



b in this case IH.I a nighl-ilying mosquito but a biting fly of the 



(Leiper) which is active by dav. 



