724 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800. 



centrically arranged. Lastly, the gorgonia which I have described as very much 

 resembling the gorgonia antipathes, proved to be similar to that species, as to the 

 membranaceous part ; but so large a portion of phosphate of lime was mixed with 

 it, as almost to approach it to the nature of stag's or buck's horn ; there is there- 

 fore great reason to consider it as a different species. 



The antipathes, which were next examined, were found to be little if at all 

 different from the horny stems of the gorgoniae. And the various sponges, which 

 were afterwards subjected to experiment, were proved to be completely formed by 

 the same membranaceous or horny substance, which became varied by the modifi- 

 cations of a more delicate construction, rather than by any essential difference in 

 composition. This series of experiments terminated with an examination of a 

 few species of alcyonium, namely, asbestinum, ficus, and arboreum ; all of which 

 were found to be composed of a soft, flexible, membranaceous substance, very 

 similar to the cortical part of some of the gorgoniae, such as gorgonia suberosa, 

 and in like manner slightly hardened by carbonate, mixed with a small portion of 

 phosphate of lime. 



From what has been said, there is reason to conclude, that the varieties of bone, 

 shell, coral, and the numerous tribe of zoophytes with which the last are con- 

 nected, only differ in composition by the nature and quantity of the hardening or 

 ossifying principle, and by the state of the substance with which it is mixed, or 

 connected. For the gluten or jelly which cements the particles of carbonate or 

 phosphate of lime, and the membrane, cartilage, or horny substance, which 

 serves as a basis, in and on which the ossifying matter is secreted and deposited, 

 seem to be only modifications of the same substance, which progressively gradu- 

 ates, from a viscid liquid or gluten, into that gelatinous substance which has so 

 often been noticed, and which again, by increased inspissation, and by the various 

 and more or less perfect degrees of organic arrangement, forms the varieties of 

 membrane, cartilage, and horn. I shall now attempt to prove what I have here 

 asserted, or at least assign the reasons which induce me to adopt this opinion ; 

 but, in so doing, I am compelled, from the close connection of the subject, to 

 anticipate the general result of part of a series of experiments, made with a view 

 to investigate the nature and composition of membrane. 



. To enter into a minute detail of these experiments, would far exceed the limits 

 of a paper like the present ; I shall therefore only mention, in a concise manner, 

 the results of those which the subject immediately requires to be brought forward*. 

 The method which first presents itself in such an investigation, is, the comparative 

 analysis of the different substances, so that their relative proportions of carbon, 

 hydrogen, and azote, should be precisely determined ; but when it is recollected 

 how long a time would be requisite for making such an immense series of analyses, 

 and how much animal substances are subject to be modified by situation in the 



* These are the experiments to which I alluded in my former paper, and which I began at the 

 request of my friend Mr. Home, soon after the experiments on the enamel of teeth, &c. — Orig. 



