400 THE ANIMAL PARASITES OF MAN 



believed to produce are lymphangitis, varicose glands, especially 

 inguinal and epitrochlear, chyluria, chylocele, lymph scrotum, 

 orchitis, abscess, and elephantiasis. The evidence that these 

 so-called "filarial diseases" are produced by F. bancrofti is (i) geo- 

 graphical and statistical ; (2) pathological. Bahr has contributed 

 evidence of the former kind from his researches in Fiji, on which 

 we may base the following statements : 



(i) The prevalence of filarial diseases is proportional to the 

 prevalence of Mikrofilaria bancrofti in the blood. Thus in four 

 villages examined by him he got the following figures: 



(2) Out of 257 people with Mf. bancrofti in the blood, 153 were 

 suffering from filarial diseases, i.e., 59 per cent. 



(3) Whereas of 672 people without Mf. bancrofti in the blood, 

 only 263 were suffering from filarial diseases, i.e., 37*6 per cent. 



(4) Again out of 41.6 people suffering from filarial disease, 153 

 showed Mf. bancrofti in their blood, i.e. t 36*7 per cent. 



It is generally assumed that all people suffering from filarial 

 disease show at some (presumably early) stage larvae in the blood ; 

 but we do not consider that this must necessarily be so. It appears 

 to us quite possible that living adult filariae may be present in the 

 body, producing disease, without their larvae appearing in the blood. 

 The absence of larvae from the blood in 63*3 per cent, of persons 

 suffering from filarial disease is, however, generally explained otherwise. 

 The adults which occur in enlarged glands, etc., get eventually 

 destroyed by inflammatory reaction, so that larvae are no longer 

 being produced, while the enlarged gland, etc., which the adults have 

 produced remains. This explanation assumes that the larvae of the 

 original worm die in the circulation or elsewhere, e.g., kidney, but 

 we have no evidence as to the duration of life of larvae in the human 

 body; but also it assumes that a person cannot be reinfected with 

 filaria, for otherwise there is no reason why the diseased should not be 

 infected in the same proportion as the non-diseased. But assuming 

 the explanation to be true, it would explain why a diseased population 

 show larvae in only about one-third of the cases. It must be borne 

 in mind also that the figures are rather small. 



Pathology. In order to explain the effects which do or may be 

 expected to occur from obstruction of lymphatics, it is necessary to 

 have an accurate knowledge of the distribution and connections of 



