198 FISHERIES OF THE ORIENTAL REGION, 



I ever saw captured in these regions is the one above-named, 

 but six others are known, mostly of small size. The fish serve as 

 food of inferior quality, and are best when salted. A good deal 

 of isinglass is derived from them, but of a poor kind. 



Of all the above fishes Polynemus indicus seems to furnish the 

 largest portion of the isinglass. The fish caught are of great 

 size, but mostly when the rivers are low. 



A few more facts about isinglass may be mentioned here. 

 What British people know by that name is the beautiful ribbon- 

 isinglass. It is made from the leaf-bladder, which is first softened 

 in the water and rolled out under high pressure into thin leaves, 

 several feet long. These again pass under a cylinder of numerous 

 revolving knives, by which 6,000 of the well-known beautiful 

 transparent fine threads are produced every minute. The Russian 

 Sturgeon isinglass is even further enhanced in value by snow- 

 bleaching, that is, whitened by being buried for a long period in 

 the snow. Pipes, purses, and lumps are fish-maws which have 

 been cleaned but not opened. These are soaked in water for two 

 or three days and the useless parts removed, then it is rolled and 

 cut into various dimensions. It is chiefly used to clarify beer and 

 other alcoholic liquids, for which gelatine cannot be employed 

 because it dissolves in hot water and alcohol, while isinglass 

 merely swells and grows white. This is a good test to distinguish 

 between the two ; for wliat is generally sold as isinglass in shops 

 is only gelatine. The transparent glutinous substance sold in the 

 bazaars as Chinese gelatine, and often mistaken for isinglass, is a 

 vegetable jelly made from rice. Many algals and lichens are 

 also made to serve the purposes of pi'oducing gelatinizing sub- 

 stances, such as Gelidium comexhin^ from which is prepared 

 what is known as 'Japan isinglass.' 



* " Gelidium, Lam. — A genus of Cryptonemiaceas (Florideous Algje), of 

 which one species {G. corneum) is very common on British shores. It has 

 a red, pinnated, homy frond, from two to six or eight inches high ; very 

 variable in the appearance of its pinnate sub-divisions. Both spores and 

 tetraspores are found on the ramules, the former in favellidia immersed in 

 swollen ramules." Harvey, Marine Alga3. 



