PHILOSOPHY OF -ZOOLOGY. 



The composition of the bones of fishes has never been in- 

 vestigated with sufficient care. It is well known, that they 

 never acquire so great a degree of hardness and rigidity 

 (with the exception, perhaps, of the bones of the ear), as 

 the bones of the mammalia or birds : hence we may safely 

 conclude from the facts connected with the process of ossi- 

 fication in other animals, that the bones of fishes abound in 

 gelatinous and cartilaginous matter, while the portion of 

 earthy or saline matter is small. The earthy salts are phos- 

 phate and carbonate of lime, and the phosphate of magne- 

 sia, the former predominating in quantity *. In one divi- 

 sion of fishes, termed the cartilaginous, the proportion of 

 earthy matter is so small, that the bones never become in- 

 durated, but continue in all the periods of the life of the 

 fish soft and flexible. These animals are, therefore, sup- 

 posed to grow during the whole course of their existence. 

 In such fishes, the bones are not Jibrous as in the osseous 

 kinds, but cellular, and the walls of the cells formed of os- 

 sified membrane. 



When the bones of some fishes are boiled in water, they 

 undergo a change of colour. This circumstance is well il- 

 lustrated in the case of the gar-fish, or sea-pike (Esox be- 

 lone), the bones of which, by boiling, become of a grass 

 green colour ; and in the bones of the viviparous blenny, 

 which experience a similar change. This alteration of co- 

 lour has fostered some of the prejudices of the vulgar, but 

 has failed, to arrest the attention of the chemist. 



The bones of fishes, when reduced to powder, are mixed 

 up with farinaceous substances, and used instead of bread, 



* In a species of Chaetodon, described by Mr BELL as the Ecan bonna 



of the Malays, many of the bones, as the ribs and spinous processes, appear 



as if diseased. They are enlarged at particular places, like tumors, which, 



when cut through, are spongy and full of .oil. Phil. Trans. 1793, p. 7. 



-Jab. vi. 



