88 Cellulose 



protozoa to consist in the main of a cellulose similar to that of 

 the Tunicata (Q. J. Micr. Soc. 1885, 445). 



These scattered observations indicate that the special 

 constitutional type or configuration of the celluloses is not con- 

 fined to those of vegetable origin. There is, of course, no reason 

 in the nature of things that the distribution of the type should 

 be limited to the plant world. It is quite possible, in fact, that 

 the animal fibres, and more generally the colloids of the animal 

 skeleton, may prove to be of similar carbon configuration to 

 that of the celluloses. A systematic investigation of such a 

 possibility has, so far as we know, not been attempted. Sugges- 

 tions have been made in, it is true, rather a wild way that the 

 silkworm is engaged in converting the cellulose of the mulberry 

 leaf into silk. It is impossible to say, a priori, how far the 

 digestive processes in an organism of this order may be destruc- 

 tive in character, but an exhaustive physiological investigation 

 would throw light on the point. It is clear, of course, that the 

 animal organism is not constructive in the same sense as the 

 plant cell, and it is an interesting subject for speculation and 

 experimental inquiry how far the vegetable products constituting 

 the food of animals are broken down by the digestive process ; 

 or, in other words, how far they may preserve their constitutional 

 features in being synthesised to * animal ' products. 



