242 



TABLE No. 34 

 RECALCULATIONS OF DATA OF TABLES 32 AND 3,3 



DATA RECALCULATED TO MOISTURE-FREE, ASH-FREE, AND PROTEIN-FREE BASIS 



The data show that each of the samples of ejected wood contains a much lower 

 percentage of cellulose and a much higher percentage of lignin than the wood from 

 which it was derived. The figures for hemicelluloses and furfural yield are less regular 

 and not readily comparable on the basis given. 



Inasmuch as it is extremely unlikely that any lignin was synthesized during 

 the passage of material through the digestive tract of the animal, the increase in 

 lignin is to be ascribed to concentration by removal of cellulose and other wood 

 constituents. Assuming that the absolute amount of lignin remaining in the residue 

 is the same as was in the original wood, we may calculate the percentage of the original 

 wood substances remaining in each of the three samples of borings by determining 

 in each case the ratio of the lignin content to that of the original wood. Thus the per- 

 centages of original wood substances in samples of borings are: 



Series 1, sample 1 



Series 1, sample 2 . 



Series II 



54.66 



X 100% = 56.1% 



X 100% = 54.7% 



X 100% = 50.9% 



The data of table 34 have been recalculated so that the constituents of the borings 

 are expressed, not on 100 parts of borings, but on 100 parts of original wood, or in 

 other words, upon the number of parts of borings corresponding to the percentages 

 found in the preceding paragraph. The results are given in table 35. 



On this basis it appears that during its passage through the animal's digestive 

 tract the wood has lost about 80 per cent of its cellulose, and from 15 to 56 per cent 

 of its hemicelluloses, including from 11 to 40 per cent of its furfural yielding constit- 

 uents, such as pentosans, etc. 



The simplest explanation of this disappearance of carbohydrate material is that 

 the cellulose and hemicelluloses of wood are partly digested by the teredo and probably 

 hydrolyzed to simple carbohydrates which the animal can use as food. 



The cellulose content and lignin content of the three samples of borings are 

 remarkably uniform (see table 34). This would seem to indicate the composition of 

 the residue which the teredo is incapable of digesting. 



