42 UKCTILIZED FISHES. 



flesh, but when prepared for leather or ornamental purposes they 

 are tanned, generally by an alum process. The ordinary method is 

 to soak the skins in fresh water four or five days, then in a lime- 

 water for from two to six days, then wash them free of lime and 

 soak them in a mixture of bran and water. They are next thoroughly 

 fleshed and put in an alum-salt solution for tAvo or three days, after 

 which they are dried and are then ready for use. 



LIVER. 



The liver, because of its rich supply of oil, has heretofore con- 

 tributed the most valuable product from the dogfish. In recent 

 years, however, petroleum products have so largely displaced the fish 

 oils that now the business of extracting dogfish oil has become 

 unprofitable in many localities where formerly it was an important 

 enterprise. Stevenson (1903) states that the livers of dogfish sell in 

 Boston and Gloucester for 25 or 30 cents per bucket of 2^ gallons. 

 During August, September, and October a bucket of livers will yield 

 6 quarts of oil. At other seasons the yield is less. Stevenson further 

 says that large quantities of dogfish oil are sold in Oregon, Washing- 

 ton, and British Columbia, owing to the high prices of other oils on 

 the Pacific coast, and much of this oil is exported. In 187G Victoria 

 exported about 00,000 gallons, at 40 cents per gallon. The annual 

 product at present is said to exceed 200,000 gallons. On the New 

 England coast the annual product probably does not exceed 10,000 

 gallons, and most of this is combined with cod oil, which is sold for 

 currjnng purposes. 



Dogfish oil has been used for lubricating and lighting purposes. 

 It burns with a bright flame and does not carbonize the wick. It 

 is also used in tanneries and in steel tempering. It makes a valuable 

 body for paints which are to be applied to out-of-door objects in 

 exposed places. In some localities it is used in the preparation of 

 wool for weaving. It has also been refined for medicinal uses and is 

 claimed by some to be as good as cod- liver oil — in fact, much of the 

 cod-liver oil sold on the market heretofore has been adulterated with 

 dogfish oil. The constituents of the latter are about the same as those 

 of cod oil, except in the quantity of iodine. When perfectly clean, 

 from fresh livers, and the oil properly refined, there seems to be no 

 reason for assuming that the dogfish-liver oil for use as a medicine 

 is inferior to the cod. 



SKELETON AND FINS. 



The skeleton and fins of the dogfish are cartilaginous and rich in 

 glue, which may be of some value. It is reported that Canada has 

 planned to reduce the dogfish plague by operating three reduction 

 plants, erected at a cost of $9,000 each, to convert the fish into fer- 



