442 Dr. J. Hjort. Observations on the Distribution of 



months of the year* showed a remarkable correspondence for the spring and 

 early summer months, i.e., the amount of fat increases in close correspondence 

 with the rise in temperature in the spring, but this relationship does not 

 continue during the late summer and autumn, thus indicating that the 

 temperature cannot be considered as the only influence concerned. 



The rise of temperature in the sea during the months of spring is of course 

 in northern waters accompanied with a great number of other phenomena, 

 viz., the increase of the intensity of light, the increased addition to the sea- 

 water of masses of fresh water from the continents carrying with them 

 inorganic and organic substances from the land and the seashore. As a result 

 of these events an " eruptive " development of plant life takes place, and 

 shortly afterwards plankton animals {i.e., copepods) develop and bottom 

 animals begin to increase their growth. 



While the development of the plants and of the small animals which 

 directly prey on them may seem easy to understand as a result of the seasonal 

 changes of the spring, the increase of the growth of larger animals like the 

 cod, the prey of which exist all the year round, seems much more difficult to 

 explain. The problem, therefore, seemed worth examination, whether the 

 decrease of growth in the autumn and the increase of growth in the spring 

 were connected with the availability of certain specific kinds of food, in other 

 words if there could be found in nature a variation of chemical qualities in 

 the food of the animals. 



The fact that the changes in the quality of the animals during the different 

 seasons have been found to be in such a close connection with changes in 

 their contents of fats raised the desirability of investigating the distribution 

 of the fat-soluble vitamines in organisms of the sea, since these vitamines 

 have been found to have such a great influence on the growth of animals. 



During my work at the Biochemical Laboratory of the University of 

 Cambridge, Prof. F. G. Hopkins had the great kindness to offer me the 

 opportunity of conducting experiments on such vitamine problems, and 

 allowed me for this purpose to have the benefit of the organisation for 

 experiments on rats which he has established at his laboratory. For the 

 purpose of such experiments during the summer 1921 1 made a collection of 

 different material of plankton and bottom animals from Norwegian waters. 

 This material was preserved in alcohol, and it was extracted in the laboratory 

 (under anaerobic conditions) with alcohol and ether, in order to extract the 

 oils for the experiments. This plan, however, had no success. The fats 

 obtained in this way were in the form of waxes, and it was soon realised that 



* Loc. cit., p. 173. 



