Field. — Utilization of Dogfish 285 



So on the one hand we are destroying' the alewife and men- 

 haden, upon which many of our fisheries depend for bait, 

 while on the other hand we are leaving in the water the 

 enemy which is destroying countless numbers of our most 

 valuable fishes. 



We have therefore made some observations to deter- 

 mine what is the practical value of the dogfish. To put it 

 very briefly, we have found that the oil in the liver is about 

 50 per cent of the weight of the liver. This oil can be sold 

 for about 25 to 35 cents a gallon, so that one dogfish would 

 ordinarily yield about 2% cents worth of oil. In addition 

 to that there is the body, which as a fertilizer is worth §27 to 

 $35 a ton at present. The dogfish then at that rate would be 

 worth about 3 cents for fertilizer, making altogether 5 : >4 

 cents. Experiments are still under way to determine 

 whether or not the peritoneum of the dogfish may be used 

 for surgical dressings. I am not prepared to go into that, 

 but it may be an important factor. The peritoneum, you 

 recall, is the delicate covering of the liver, intestines, etc., 

 which can be separated as a very thin, delicate membrane. 



Finally, and perhaps most important, we have made 

 some experiments to ascertain the value of the eggs of the 

 dogfish. Each female dogfish yields from four to eight 

 eggs; how often we do not know, but probably two or three 

 times a year. These eggs are retained in the body of the 

 dogfish until they are hatched. The young are born alive. 

 We find that the eggs can be used by tanners as hen's eggs 

 are used. For a practical demonstration we furnished the 

 tanners with about 75 pounds of the eggs, and we received a 

 report that they could be used the same as hen's eggs. You 

 know that in preparing glove leather it is important to get 

 the oil into the leather in such a way that the leather will no1 

 remain greasy. For this purpose they make an emulsion 

 of the oil and treat the skin with it. Hen's eggs are used by 

 stirring them up in the oil, and thus used it is found that one 

 dogfish egg is equal to two hen's eggs. In other words, 

 one dosfish ees: will emulsifv as much oil as will two hen's 



