and Observations on the component Parts of Membrane. 369 



The animal mucilage which I chiefly employed in these 

 experiments, was obtained from the Corallina officinalis, as I found 

 it to be pure, and not partly modified into gelatin or animal 

 jelly.* But Mr. Bouvier asserts, that he obtained the latter 

 substance ; -f and this appears to me very probable ; for mucilage 

 may predominate in this coralline at one period, and gelatin 

 or jelly at another, just as is found to be the case with other 

 animal substances; for it is known, that in young animals 

 mucilage is abundant, and becomes diminished as these increase 

 in growth and age. Hence there is every reason to conclude, 

 that the substance which in the very young animals was at first 

 mucilaginous, becomes progressively more viscid, and assumes 

 the characters of gelatin ; which, as animals increase in age, is 

 known to become more and more viscid, as has been already 

 mentioned in the foregoing pages. I am inclined, therefore, to 

 consider mucilage as the most attenuated, and as the lowest in 

 order, among the modifications of gelatin. 



As the qualities of gelatin are so various, so the properties of 

 the substances in which it is present as a component part, are 

 much influenced by it; and when, for example, the skins of 

 different animals were compared, I have always found that the 

 most flexible skins afforded gelatin more easily, and of a less 

 viscid quality, than those which were less flexible, and of a 

 more horny consistency. 



* By this I mean, that the mucilage had not acquired the degree of viscidity 

 requisite to form a gelatinous substance. The expression which I have employed, is 

 not therefore to be understood as alluding to any essential difference in composition, 

 but only to denote some variation in the degree of consistency ; for the whole may be 

 comprehended under the term gelatin, of which, mucilage may be regarded as one 

 extreme, and the strongest and most viscid glue as the other. 



t Annates de Cbimie. Tom. VIII. p. 311. 



3 B 2 



