386 University of California Publications in Zoology [Vol. 22 



CHEMICAL CONSIDERATIONS 



Indirect evidence, however, must of necessity be inconclusive. 

 The need of definite experimental proof lias suggested an approach 

 to the problem from the chemical point of view. It should be possible 

 to determine experimentally (1) whether or not the enzymes of 

 Teredo are capable of acting upon any of the constituents of wood, or 

 (2) whether or not the wood particles are chemically changed in their 

 passage through the digestive tract. 



The first of these alternatives has been selected for investigation 

 by Harrington (1921), who has shown, though not so conclusively as 

 might be desired, that a certain enzyme or enzymes extracted from 

 excised livers of Teredo norvegiea will act on sawdust to produce 

 glucose. Since the liver extract failed to reduce pure cellulose, 

 Harrington concludes either that the enzymes were not present in 

 sufficient concentration, or that action on the wood was limited to 

 hydrolysis of the hemicelluloses, which are notably more easily broken 

 down than pure cellulose, with the further alternative that "there 

 may be other substances present in wood which are necessary as 

 co-enzymes to the ferment in question." 



The present writers would suggest the possibility that the liver 

 enzymes are not the only digestive ferments acting in the intestinal 

 tract of Teredo; there may be enzymes from the crystalline style 

 (Nelson, 1918, pp. 93, 107) or other parts of the digestive system, 

 which are the necessary co-enzymes in the process of hydrolysis of 

 wood. It is entirely within the limits of probability that a fluid 

 capable of hydrolyzing cellulose may be poured out in the region of 

 the foot, so as to serve the double purpose of softening the wood to 

 facilitate boring and of preparing a part of it for absorption. 



It is hoped that Harrington will press these interesting physio- 

 logical investigations farther along the lines he himself has suggested. 

 In the meantime, it has seemed to the present writers that very 

 definite results might be obtained from the second method of investi- 

 gation mentioned above, namely, by extracting and comparing the 

 chemical constitution of the borings with that of the original wood, 

 thus arriving at both a qualitative and quantitative determination of 

 such changes as may take place during passage of the borings through 

 the digestive tract. 



