112 



necrotic areas would produce a corresponding tissue reaction, 

 and so the tumour would continue to enlarge or grow. 



The chronicity of the tumour is due mainly to three 

 factors, whilst in some cases there is a fourth. In the first 

 place the slow diffusion of the necrosis-producing substance, 

 which probably has its origin in the degenerating or autolysing 

 larva, tends to produce a slow development of the necrosis, 

 and to maintain it for some time. Secondly, the type of 

 necrosis is that which is not readily absorbed or removed. The 

 types of necrosis, or the characteristic changes of necrosis, 

 depend mainly upon the intracellular enzymes. The necrosis- 

 producing substance in this case must lead to an early destruc- 

 tion of the autolytic enzymes of the cells, thus preventing 

 further degenerative changes in the dead cells. 0-) Thirdly, 

 because of the lack of chemotactic substances no neutrophile 

 leucocytes enter to remove the dead tissue. Fourthly, there is 

 the possibility of a super-infection. If a tumour has resulted 

 from an infection of a wound, or after ulceration of a tumour 

 has taken place, the possibility of the entry of fresh larvae 

 must be considered. This super-infection has been very dis- 

 tinctly observed in tumours examined from cases occurring in 

 the British Solomon Islands. 



There seems to be no doubt that the presence of the 

 larvae in the subepithelial tissues is accidental. The larvae 

 apparently have no power of completing their life-history, for 

 even in the earlier lesions they always show retrogressive 

 changes, while in the older lesions one may be unable to detect 

 anything but a few worm canals, empty or containing a 

 granular debris. 



However, soon after their introduction the larvae must 

 exhibit some progressive movement, for they penetrate to some 

 depth into the subepithelial tissues, and, in the looser tissues, 

 such as are found in the sheath, they become more dispersed. 

 But this power of penetration is distinctly limited, and the 

 larva is soon unable to maintain its life, probably on account 

 of an inability to obtain a suitable food supply. 



The larva cannot correctly be called a parasite, for a 

 parasite may be defined as a living organism which takes up 

 its abode on or within other living organisms for the purpose 

 of obtaining food. 



(i) That absorption of dead tissue depends mainly upon the 

 completeness or incompleteness of the destruction of the intra- 

 cellular enzymes is illustrated by the following experiment : — Two 

 pieces of fresh normal tissue, one heated to 100° C, and the other 

 untreated, when placed in the abdominal cavity of the same species 

 undergo very different changes. The unheated tissue soon under- 

 goes autolytic changes and is absorbed, whereas the heated tissue, 

 although dead, undergoes no autolytic changes, and is very slowly 

 absorbed. 



