326 PHILOSOPHY OF ZOOLOGY. 



held in high estimation in the northern islands of this 

 country. But it is chiefly in the manufacture of the sub- 

 stance called ISINGLASS, that the sounds of fishes are ex- 

 tensively employed. The sounds of various kinds of stur- 

 geon are chiefly made use of for this purpose. The exter- 

 nal membrane is removed, and the remaining part is cut 

 lengthwise, and formed into rolls, and then dried in the open 

 air. The sounds of cod and ling are frequently employed 

 as a substitute for those of the sturgeon. They require some 

 dexterity to separate them from the back-bone. But when 

 the membranes are well scraped on both sides, steeped for 

 a few minutes in lime-water to absorb the oil, and then 

 washed in clean water, and dried, they form an isinglass of 

 considerable value *. 



Isinglass consists almost entirely of gelatine, and is used 

 either as food, Or for the purpose of fining liquors. 500 

 grains of it yielded to HATCHET, by incineration, 1 .5 grains 

 of phosphat of soda, mixed with a little phosphat of lime. 

 An inferior kind is manufactured from the bones, fins, and 

 useless parts of fishes. These materials are boiled in wa- 

 ter, the fluid skimmed and filtered, and afterwards concen- 

 trated, until it readily gelatinizes on cooling. This kind is 

 much used in various manufactures, and might be procur- 

 ed in considerable quantity at all the fishing stations in this 

 country, where the materials abound, but which are at 

 present left as a nuisance on the adjoining beach ( 



The BRAIN of fishes is of a less compact texture than 

 the corresponding organ in the higher classes. In some 



* Phil. Trans. 1773, p. 1. 



f The value of these materials to the agriculturist is properly appreciated 

 in some places, as at Wick in Caithness, where, by means of the herring- 

 guts formed into a compost with earth, and then applied as manure, the 

 ground in the neighbourhood has been fertilized, on which, a few years be- 

 fore, the very heath was of dwarfish growth. It would be fortunate if the 

 natives of Orkney and Zetland were to imitate the example of those at Wick* 



