240 The Commercial Products of the Sea. 



A. Lichtensteinii ; also A. maculosiis, and A. oxyrhynchus 

 from North America. 



Isinglass has, in a measure, had its consumption checked 

 by its high price, and substitutes are employed, such as 

 gelatine (of which it is itself the purest form). It is of a 

 highly nutritious and unirritating nature, admirably adapted 

 for the sick room, and the preparation of some forms of 

 confectionery and cookery, besides being employed both 

 externally and internally in medicine, in the preparation of 

 court plaster, in some arts and manufactures, but more 

 extensively for clarifying or fining wines and beer. The 

 brewer employs it as follows : — Some, having been finely 

 divided, is dissolved in sour beer, to the consistence of a 



Fig. 18. 



The Sturgeon. 



thick mucilage, and a portion is added to the fluid which 

 it is intended to clarify, and after a longer or shorter period, 

 suspended substances subside. Some suppose that all 

 floating particles become entangled in the isinglass, and, 

 uniting with it, form an insoluble compound which becomes 

 precipitated ; others, that when dissolved in a fluid it 

 lessens its affinity for the suspended particles, which, being 

 thus set free, subside. 



The finest description of isinglass is thin, tough but 

 flexible, white, semi-transparent, and destitute of both taste 

 or smell ; it almost entirely dissolves in boiling water, and 



