54 HABITS OF WORMS. CHAP. I. 



to such castings not having been recently 

 ejected; for some which were at first acid, 

 were on the following morning, after being 

 dried and again moistened, no longer acid ; 

 and this probably resulted from the humus 

 acids being, as is known to be the case, easily 

 decomposed. Five fresh castings from worms 

 which lived in mould close over the chalk, 

 were of a whitish colour and abounded with 

 calcareous matter; and these were not in 

 the least acid. This shows how effectually 

 carbonate of lime neutralises the intestinal 

 acids. When worms were kept in pots filled 

 with fine ferruginous sand, it was manifest 

 that the oxide of iron, with which the grains 

 of silex were coated, had been dissolved and 

 removed from them in the castings. 



The digestive fluid of worms resembles in 

 its action, as already stated, the pancreatic 

 secretion of the higher animals ; and in these 

 latter, " pancreatic digestion is essentially 

 " alkaline ; the action will not take place 

 "unless some alkali be present; and the 

 " activity of an alkaline juice is arrested by 

 "acidification, and hindered by neutraliza- 



