FISH PRODUCTS 131 



for use as manure. In Germany in 1918 herrings' 

 heads were removed by the curers to be utilized for the 

 production of oil, albumen, and phosphate of lime. 

 The herring meal contained up to 50 per cent of albumen 

 and calcium phosphate, the latter being obtained from 

 the bones and heads. The albumen was extracted 

 chemically and prepared for human consumption. 

 The oil was extracted with benzol or other solvents, 

 and, after hardening, was used in the manufacture of 

 butter substitutes. Fish waste or offal is fed into a 

 continuous cooker. This cooker consists essentially 

 of a long, cylindrical vessel, through which runs a hollow 

 steel shaft on which are mounted perforated radial 

 vanes in such a way that the whole arrangement forms 

 a spiral conveyor. By means of the hollow shaft and 

 vanes, steam is blown into the mass of fish waste as it 

 travels slowly through the vessel, so that it is completely 

 cooked and disintegrated by the time that it emerges 

 at the other end. 



The cooked mass is then fed into a press in which a 

 screw conveyor urges it through a gradually tapering 

 cylinder with perforated sides. In this way the oil is 

 extracted from it, and it is then dried and disintegrated 

 by a rotary drier. 



There is always a little residual oil in fish manure 

 that tends to delay its decomposition in the soil. It is 

 important, therefore, that the oil be removed as 

 completely as possible. 



Dry fish manure requires careful storing, as the 

 presence of this, small amount of oxidizable oil tends to 

 promote spontaneous combustion. 



In addition to its value as a fertilizer, the high content 

 of protein (albumen) namely, 50 per cent makes fish 

 meal a suitable food for live-stock and poultry. 



The commercial importance of this industry will be 



