62 VEGETABLE PARASITES 



nails, is simply mechanical, and as readily ex- 

 plained as the migration of any other foreign 

 bodies from one place in the body to another. 

 The vegetable growth pushes aside the animal 

 tissue. Pressure always produces absorption in 

 the animal organism ; hence the spores, in penetrat- 

 ing and pushing deeper into the underlying tissue, 

 cause atrophy of the fibres of the skin in those 

 places. The cells contaiiiing the fat disappear, 

 as a section of the skin will show, and a cavity is 

 formed which is thinner at the spot where the 

 growing parasite has fixed itself. We have, there- 

 fore, now seen where these vegetable spores come 

 from, they being on every substance the skin comes 

 in contact with, even the air, in which they float ; 

 and we have, also seen how they penetrate the 

 special tissues we are considering. Let us study, 

 now, the effect of their presence and growth in 

 these tissues. 



The mere presence of the vegetable parasite in 

 the epidermis is not of itself an injury, since it 

 produces only slight thickening and some discol- 

 oration, with a branny condition of the surface. 

 Unfortunately, however, itching is also caused, 

 sometimes quite excessive, rendering the conse- 



