UTILIZATION OF THE FISH WASTE OF THE PACIFIC OCFAN. 21 



ments necessary for the further development and ripening of the roe 

 are supplied through the metamorphosis of the materials already 

 stored up within the body of the fish. The weight of the roe prob- 

 abty about equals that of the other waste produced with it ; and that 

 of the roe, fins, and tail, combined, probably equals that of the head. 

 The roe, then, according to this estimate, makes up about 25 per cent 

 of the weight of the waste produced in the cannery; and the head, 

 according to the same estimate, about 50 per cent. Therefore about 

 one-half of the materials designed for hypothetical rendering plants 

 would be in the form of compact lumps, rather clean in nature, and 

 easily handled (the heads). In this connection it may be said that 

 during seasons of abundant materials some of the rendering plants 

 now in operation make a practice, so far as possible without compli- 

 cating the methods, of collecting only the heads. As the material is 

 being loaded upon the scow for transportation to the rendering plant, 

 streams of water are allowed to play over it until most of the finer 

 matter is washed out and practically only the heads remain. This 

 practice is followed because of the greater facility with which the 

 heads can be rendered. The roe contains more gelatinous material, 

 which adds to the difficulties of pressing. 



Xn additional though small amount of waste is found in the water 

 from the " slimers' " tables. This consists of the small strings of the 

 viscera and of pieces of fins still adhering to the fish after having 

 passed through the mechanical cleaner, and of the clots of blood 

 which lie along the dorsal portion of the body cavity. 



The entire mass of waste, with the exception of the heads, is 

 moved by streams of water. Any system of collecting it entirely 

 must depend on handling — to begin with, at least — the entire volume 

 of water. It is a happy circumstance that all of this material has 

 a higher specific gravity than has water, so that a complete separa- 

 tion of it from the water is possible simply through settling. This 

 applies to every part of the waste, except, of course, the dissolved 

 blood. The dilution of this solution makes its treatment for the 

 recovery of the blood of doubtful economy. Since the final elimina- 

 tion of this large volume of water is so easy, no particular advantage 

 is to be gained from the reduction of its volume so long as that 

 reduction involves the loss of valuable solids. For that reason it 

 probably would prove most advantageous to include the entire 

 volume of water used in the various cleaning operations in any 

 process for the collection of the by-products. In other words, since 

 the separation of the solids from the liquids is so easily accomplished 

 by simply permitting the former to settle out, but very little more 

 expense would be involved in using a large than a small volume. 



The physical composition of the waste produced in the cleaning 

 house, then, is the heads, forming large lumps, the tails in smaller 



