Chap. L CALCIFEKOUS GLANDS. 4)3 



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 

 seci'etion 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- 

 " tion."* Therefore it seems highly probable 

 that the innumerable calciferous cells, which 

 are poured from the four posterior glands 

 into the alimentary canal of worms, serve to 

 neutralise more or less completely the acids 

 there generated by the half-decayed leaves. 

 We have seen that these cells are instantly 

 dissolved by a small quantity of acetic acid, 

 and as they do not always suffice to neu- 

 tralise the contents of even the upper part of 

 the alimentary canal, the lime is perhaps 

 acrgregated into concretions in the anterior 

 pair of glands, in order that some may be 



♦ M. Foster, Ibid., p. 200. 



