718 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800.* 



wards by infusion of oak bark. The antipathes being then boiled with lixivium 

 of caustic potash, was completely dissolved, and formed the animal soap of Mr. 

 Chaptal. 



Antipathes myriophylla. — This was subjected to experiments like those above 

 related, and as the effects were the same, it is not necessary that particular men- 

 tion should here be made of them. As the specimens of these antipathes were 

 small, I was not able to make any additional experiments ; but what has been said 

 sufficiently proves how much they resemble the horny stems of the gorgoniae. 



Sponges. — Many species of sponge were examined, but as little or no essential 

 difference was found in the results, I shall include them all in what is now to be 

 related. The following species, with many others not described, were subjected 

 to experiment. Spongia cancellata. Sp. oculata. Sp. infundibuliformis. Sp. 

 palmata. Sp. officinalis. When the sponges had been immersed in nitric acid, 

 diluted with 3 measures of distilled water, during 14 or l6 days, the acid became 

 pale yellow, and was changed to an orange colour by the addition of pure am- 

 monia. The sponges which had been thus steeped in the dilute acid, became, 

 like the gorgoniae, more or less transparent, and were considerably softened. In 

 this state, if they were touched with ammonia, the part thus touched became of 

 a deep orange colour, inclining to a brownish red ; and when much softened by 

 the acid, if afterwards immersed in ammonia, they were completely dissolved, and 

 formed a deep orange-coloured solution*. When digested with boiling distilled 

 water, the sponges afforded a portion of animal jelly or gelatin, which was pre- 

 cipitated by infusion of oak bark. The fine and more flexible sponges yielded 

 gelatin in greater abundance, and more easily, than those which were coarse and 

 rigid. The gelatin was gradually and progressively imparted to the water, and 

 seems, even in the same sponge, to be a constituent principle, of different degrees 

 of solubility ; and it must be noticed, that in proportion as the sponges, parti- 

 cularly those which were soft and flexible, were deprived of this substance, in the 

 like proportion they became less flexible and more rigid, so that the remaining 

 part, when dry, crumbled between the fingers ; or, when moist, was torn easily, 

 like wetted paper. As the above properties prove that sponges only differ from 

 the horny stems of the gorgoniae, and from the antipathes, by being of a finer 

 and more closely woven texture-f-, so this similarity will be corroborated by the 

 following remarks. When exposed to heat, they yielded the same products, the 

 same smell, and afforded a similar coal, which by incineration left a very small 

 residuum, consisting chiefly of muriate of soda, occasionally mixed with some 

 carbonate of lime, which was also often discovered when the recent sponges were 



* The same effects were observed when the horny stems of the gorgoniae, antipathes, &c. which 



had been long steeped in dilute nitric acid, were immersed in pure or caustic ammonia. f This is 



particularly to be observed by comparing the coarse sponges, such as spongia cancellata, with the 

 finely reticulated parts of certain gorgoniae, especially those of gorgonia flabellum, when divested of 

 the external membrane. — Orig. 



