94 TROPICAL MEDICINE AND HYGIENE 



by leading to inflammation or suppuration, events that 

 seem sometimes to be associated with the death of the 

 worm, would not explain those cases in which the onset 

 is gradual, nor the steady increase in the lymphatic 

 oedema following a single attack of " rose." They might 

 explain some of the cases, especially those associated with 

 obstruction of the main lymphatic trunks or in the 

 glands. In some cases where these events have been 

 known to occur in accessible portions of the body 

 no elephantiasis has followed. These methods would 

 account for the absence of filarial embryos, as the adult 

 worms in the region of the block are either dead or are 

 enclosed in an organized blood-clot, or in inflammatory 

 exudation. In any case the embryos discharged into the 

 lymph behind the obstruction would not be able to get 

 into the blood-stream. 



The main lymphatic systems are normally separated 

 from each other, though there is free anastomosis of the 

 lymphatic channels at the periphery of the system. This 

 renders it improbable that a single local obstruction 

 should cause such extensive progressive oedema. In 

 chronic diseases, as in carcinoma, we know that a col- 

 lateral lymph circulation may be established. Enlarged 

 hard glands are so commonly present in cases of elephan- 

 tiasis above the affected area that it is probable that 

 much, if not the main part, of the obstruction takes 

 place in them. 



In the scrotum where the lymph escapes through 

 several channels no single obstruction could produce the 

 results so commonly seen. Multiple obstructions involv- 

 ing a number of small lymphatic vessels would be 

 necessary to cause sufficient obstruction. Such gross 

 obstructions as those directly due to the living or dead 

 adult filariae would therefore explain only some of the 

 phenomena. 



Manson has suggested a hypothesis which at first sight 

 seems far-fetched, but on closer inquiry appears to pro- 

 vide a fairly complete explanation of the observed 



