SOLID PARTS OF ANIMALS. 



of tliin membranous substances, which still retain the form of the 

 shell. From Mr Hatchett's experiments, we learn that these 

 membranes have the properties of coagulated albumen. Mother- 

 of-pearl shells, then, are composed of alternate layers of coagu- 

 lated albumen and carbonate of lime, beginning with the epider- 

 mis, and ending with the last-formed membrane. The animals 

 which inhabit these shells increase their habitation by the addi- 

 tion of a stratum of carbonate of lime, secured by a new mem- 

 brane ; and as every additional stratum exceeds in extent that 

 which was previously formed, the shell becomes stronger as it 

 becomes larger.* 



Oyster shells, according to the analysis of Bucholz and 

 Brandes, are composed of 



Albuminous matter, . 0-5 



Lime, . . 54-1 



Carbonic acid, . .44*5 



Phosphate of lime, . 1 '2 



Alumina, . . 0-2. 



100-5 f 



The scales on the outside of oyster shells, according to the 

 analysis of John, are composed of 



Animal matter soluble in water with ~i 

 common salt and trace of phosphates, ) 

 Ditto insoluble in water, . . 10 



Carbonate of lime, . . .87 



loot 



Though this in general is the structure of the mother-of-pearl 

 shells, yet there is a considerable difference between the propor- 

 tion of the component parts and the consistency of the albumi- 

 nous part. Some of them, as the common oyster- shell, approach 

 nearly to the patellae, the albuminous portion being small, and 

 its consistence nearly gelatinous ; while in others, as the Haliotis 

 iris, the Turbo olearius, the real mother-of-pearl, and a species of 

 fresh-water muscle analyzed by Hatchett, the membranes are 

 distinct, thin, compact, and semitransparent Mother-of-pearl 

 contains 



Hatchett, Phil. Trans. 1799, p. 317. t Gmelin's Handbuch, ii. 1477. 

 \ Chem. Schr. vi. 103. Hatchett, Phil. Trans. 1799, p, 317. 



