Fat-Soluble Vitamines in Marine Animals and Plants. 441 



the winter season. Corresponding to the summer and winter zones, which 

 are to be seen on the scales of the fish, we find a periodicity in the increase of 

 length and weight of the fish, and a change in the quality of the fish at the 

 different seasons of the year. 



The changes in the " quality " of the fish were very early observed to be 

 associated with the changes occurring in the content of fat. Chemical 

 analyses were made by Mr. H. Bull of the fat contents of herrings and sprats 

 at different months of the year,* and from these observations the conclusion 

 was drawn that " the supply of fat increases during the summer and is- 

 consumed during the winter, while water is excreted in the summer and 

 assimilated in winter. During the winter, part of the dry matter in the 

 system is consumed and replaced by water, so that no great loss in weight is 

 apparent. The quality of the fish, however, is considerably affected." . 



In the herring this is very apparent, the fat being deposited in a special 

 peritoneal fat organ (by Norwegian fishermen called the " ister "), which is 

 especially developed in summer and in the young year classes which have not. 

 yet developed their generative organs. As stated in the paper, the contents 

 of the fat organ " varies with the age of the fish, the development of the 

 genital organs, in particular, being a factor of great significance. In addition 

 to this, the quality of ister varies greatly according to the time of year ; this 

 applies not only to the ister itself, but also to the contents of fat on the whole 

 as shown by chemical analysis." 



In the cod the changes in quality are most easily demonstrated by the 

 inspection of the size of the liver, the contents of which, so far as some 50 per- 

 cent, is concerned, consist of the " cod-liver oil." Besides by chemical 

 analyses, the liver has been studied by means of weighings. The livers of 

 cod of different sizes (in groups of different lengths) have been weighed at 

 different times of the year, and it has been found that the liver of the full- 

 grown cod during the summer season, when the fish was feeding, weighed no 

 less than three times as much as in the winter during the spawning season. 

 "The greatest 'depreciation' in the quality of the cod takes place during 

 their stay on the Lofoten Banks, where the genital organs arrive at full 

 maturity and spawning takes place."f 



These observations naturally led to a consideration of the problem of the 

 conditions which determine the great changes in the growth of the fish 

 themselves, and particularly in the organs in which the reserve material (fats) 

 are stored. A comparison between the amount of fat in the sprat of the 

 west coast and the mean surface temperature of the sea for the different 



* See loc. cit., Chapter V. 

 t Loc. cit., p. 195. 



