SOLID PARTS OF ANIMALS. 



CHAPTER VII. 



OF ZOOPHYTES. 



MANY of the substances called zoophytes have the hardness 

 and appearance of shell or bone, and may therefore be included 

 among them without impropriety. Others, indeed, are soft, and 

 belong rather to the class of membrane or horn ; but of these 

 very few only have been examined. Indeed scarcely any '^chemi- 

 cal experiments have been published on these interesting subjects, 

 if we except the dissertation by Hatchett, in the Philosophical 

 Transactions for 1800, which has been so often quoted. From 

 this dissertation, and from a few experiments of Merat-Guillot, 

 we learn that the hard zoophytes are composed chiefly of three 

 ingredients : 1. An animal substance of the nature of coagulat- 

 ed albumen, varying in consistency ; sometimes being gelatinous 

 and almost liquid, at others of the consistency of cartilage. 2. 

 Carbonate of lime. 3. Phosphate of lime. 



In some zoophytes the animal matter is very scanty, and phos- 

 phate of lime wanting altogether ; in others the animal matter is 

 abundant, and the earthy salt pure carbonate of lime ; while in 

 others the animal matter is abundant, and the hardening salt a 

 mixture of carbonate of lime and phosphate of lime ; and there 

 is a fourth class almost destitute of earthy salts altogether. Thus, 

 there are four classes of zoophytes ; the first resemble porcelane- 

 ous shells, the second resembles mother-of-pearl shells, the third 

 resembles crusts, and the fourth horn. 



1. When the Madrepora virginea is immersed in diluted nitric 

 acid it effervesces strongly, and is soon dissolved. A few gela- 

 tinous particles float in the solution, which is otherwise transpa- 

 rent and colourless. Ammonia precipitates nothing ; but its 

 carbonate throws down abundance of carbonate of lime. It is 

 composed, then, of carbonate of lime and a little animal matter. 

 The following zoophytes yield nearly the same results : 



Madrepora muricata. 



labyrinthica. 



Millepora cerulea. 



alcicornis. 



Tubipora musica, 



2. When the Madrepora ramea is plunged into weak nitric 



