THE IMPENETRABLE SEA 



and in all parts of the world, and has the popular name 

 of ''rock salmon". But the phrase ''shark and chips" has 

 not yet become colloquial. 



Another highly important product of the shark fisheries 

 is shark oil. Most of it is extracted from the fish's liver, 

 yet many of the encyclopaedias published in the nine- 

 teenth century described the liver of the shark not merely 

 as "uneatable" but as "very poisonous". Much of the oil 

 is used for mixing with cod liver oil — not as an adulterant 

 but because shark oil contains twice as much iodine as 

 any other, so that cod liver oil is greatly improved by its 

 addition. As much as eighteen gallons of oil have been 

 obtained from the liver of a single shark. The oil is also 

 used in many other ways — for cooking purposes, in 

 leather dressing, and as a lubricant, etc. The liver itself 

 is ground into poultry food. Apart from the liver, the 

 flesh of sharks yields an extract which compares favour- 

 ably with extract of beef for nutritive purposes. 



Dyes of many kinds are manufactured from sharks' 

 bodies. The bones are ground up to make meal for cattle 

 and chickens. Glue is yet another substance that comes 

 from their carcasses. Some idea of the value of the shark in 

 the world's markets may be gained from the fact that the 

 shark-fin trade of other nations with China alone, in pre- 

 war times, necessitated the capturing of over a hundred 

 thousand sharks annually. 



Skates and rays are among the most hideous and 

 repulsive of all fish. Some of them attain enormous 

 dimensions, while many are dangerous because of the 

 wounds inflicted by the spines of their tails. The true rays 

 lead a sedentary life, moving slowly over the floors of the 

 sea-shelves and seldom rising to the surface. The tail of 

 the ray has almost entirely lost its function as an organ 

 of locomotion — it acts as a simple rudder. The fish pro- 

 gresses by means of its pectoral fin, which maintains an 

 undulating motion. Nearly all rays lay eggs. Many of 

 them ascend rivers to a considerable distance. 



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