52 HABITS OF WORMS. CHAP. I. 



decay generate an abundance of various kinds 

 of acids, which have been grouped together 

 under the term of humus acids. We shall 

 have to recur to this subject in our fifth 

 -chapter, and I need here only say that these 

 acids act strongly on carbonate of lime. The 

 half-decayed leaves which are swallowed in 

 .such large quantities by worms would, there- 

 fore, after they have been moistened and 

 triturated in the alimentary canal, be apt to 

 produce such acids. And in the case of 

 .several worms, the contents of the alimentary 

 canal were found to be plainly acid, as shown 

 by litmus paper. This acidity cannot be 

 .attributed to the nature of the digestive fluid, 

 for pancreatic fluid is alkaline ; and we have 

 seen that the secretion which is poured out of 

 the mouths of worms for the sake of pre- 

 paring the leaves for consumption, is likewise 

 alkaline. The acidity can hardly be due to 

 uric acid, as the contents of the upper part of 

 the intestine were often acid. In one case 

 the contents of the gizzard were slightly acid, 

 those of the upper intestines being more 

 plainly acid. In another case the contents of 



