22 BULLETIN 908, U. S. DEPARTMENT OF AGRICULTURE. 



The gills and digestive tract harbored bacteria as long as feed was 

 present, but apparently as soon as all feed and waste products were 

 eliminated these portions freed themselves of bacteria. Portions of 

 cod, rockfish, bass, and alewives were also examined. The alewives 

 alone were obtained with no feed present, and out of 72, 47 con- 

 tamed neither feed nor bacteria. B. coli and B. WalfiscTirauscJibrand 

 were isolated from the cod. The flesh was free from bacteria in 

 practically every instance. 



Chemical Composition of the Feed of Herring. 



The crustaceans, to which group of sea life the feed of the sea her- 

 ring belong, differ in composition from meats and fish in having a 

 large proportion of the carbohydrate glycogen present in the liver. 

 This is suggestive in connection with the rapid formation of gas 

 observed in decomposing feed, such as schizopods and copepods. 

 Undoubtedly the composition of the feed is of such a nature as to 

 furnish an excellent medium for the growth of gas- and nongas-pro- 

 ducing bacteria. 



In an investigation of the chemical composition of plankton, K. 

 Brandt (4) obtained the following results on analyzing material which 

 consisted almost entirely of copepods: 



Table 5. — Chemical composition of copepods (dry basis) (Brandt). 



Per cent. 



Protein 58. 80 



Fat 7. 40 



Carbohydrates (by difference) 22. 88 



Ash. . . ." 10. 92 



Composition of ash : 



Silica (Si0 2 ) 2.31 



Common salt (NaCl) 1. 49 



Other salts 7. 12 



He found the composition of the dry substance of copepods, which 

 included varieties taken from fresh water, to be as follows: 



Table 6. — Average composition of copepods (dry basis) (Brandt). 



Per cent. 



Protein 59. 



Chitin 4. 7 



Fat 7.0 



Carbohydrates 20. 



Ash 9.3 



The results of the chemical analyses, made during this investigation 

 on the feed of the sea herring, to determine the rate of decomposition 

 are given in Table 7. The total volatile nitrogen, ammonia, and 

 amines were determined as the indices of decomposition when the 

 feed, copepods, and schizopods were allowed to spoil under the most 

 favorable conditions in an incubator. The determination of the total 



