202 VITALITY AND EFFICIENCY WITH RESTRICTED DIET. 



With other animals and, indeed, with fishes, pronounced changes in 

 nutritional level are frequently observed, particularly prior to the 

 breeding season. Thus Parker^ specially emphasizes the prime 

 condition of the bull seals in the Pribilof Islands at the beginning of the 

 mating-season. Throughout this time, according to Parker, no food 

 is taken and the physical combats of the mature animals in the various 

 rookeries are very fierce; at the end of the breeding-season the bulls are 

 distinctly in a depleted muscular condition. 



"The bulls, as a result of their incessant activities, are in a state of extreme 

 emaciation. Many of them have been on the beaches from May, and during 

 the period between the time of their arrival and the end of July or early part 

 of August, they touch no food. This fast of well over two months, coupled 

 with their incessant activity, drains them of all their stored energy. Their 

 fat disappears and they are reduced almost to skin and bones. In this state 

 they may be driven off a rookery without resistance and they soon return to 

 the sea to begin the winter migration. During this period they feed and 

 fatten in preparation for the coming season." 



Miescher's notable observations^ on the migration of the salmon in 

 the Rhine and the severe drafts upon muscular tissue primarily made 

 for transformation into testicular or ovarian tissue are all called to 

 mind as provisions of nature for marked transitions in nutritional level. 

 Thus, Miescher shows that the salmon, after coming to the Rhine from 

 the sea, virtually starve. Yet the generative organs of both male and 

 female develop greatly, this being at the expense of the muscles, which 

 may lose 55 per cent of their weight. Even after 5 to 15 months' fast 

 in fresh water, during which time they lay their eggs, Miescher found 

 fat globules in the muscle-cells of salmon. 



In addition to the classical work of Miescher, to whom we have been 

 indebted for practically all of our knowledge on the composition of the 

 migrating salmon, it is a great pleasure now to be able to cite two 

 especially fine pieces of American research, that by Greene^ and more 

 recently that by E. D. Clark and L. H. Ahny,^ who fully confirm and 

 extend Miescher's observations. 



In view of this adjustment to conditions, it is somewhat surprising 

 that the popular conception of emaciation and nutritional level should 

 be so antagonistic to any reduction in body-weight. In reahty, there is 

 no biological reason why there should not be at least a periodic change 

 of considerable degree in the nutritional level with man. Since these 

 changes in the nutritional level may have profound significance in re- 

 production, judging from the lower animals, it thus becomes impor- 



» Parker, Scientific Monthly, May, 1917, p. 393. 



2 Miescher-Reusch, F., Statistische und biologische Beitrage zur Kenntniss vom Leben dea 

 Rheinlachses im Susswasser, Internat. Fischerei-Ausstellung, in Berlin, 1880, p. 154; 

 see also Miescher-Reusch, Die histochemischen und physiologischen Arbeiten, Leipsic, 

 1897, p. 116. Cited by Clark and Almy, Journ. Biol. Chem., 1918, 33, p. 497. 



2 Greene, Journ. Biol. Chem., 1912, 11, p. xviii; see also same journal, 1918, 33, p. xiii. 



♦ Clark and Almy, Journ. Biol. Chem., 1918, 33, p. 483. 



