of the Salmon in Fresh Water. 173 



sea (p. 95). Not only is the tissue between the individual 

 fibres loaded with fat, but, as shown by Mr. Mahalanobis (p. 106), an 

 intrafibrous or interfibrillar accumulation of fat occurs. In the river, 

 as the season advances, this accumulated fat is steadily got rid of by 

 the muscle. There is no reason to suppose that anything of the nature 

 of a degeneration occurs. The 'fat is simply excreted from the muscle 

 to supply the fat of the growing genitalia, or used in the muscle as a 

 source of energy. 



In the muscles the fatty acids are chiefly in the form of ordinary fats. 

 In the ovaries and testes, on the other hand, the fatty acids are largely 

 combined with phosphorus as lecithin. An important decomposition 

 and reconstruction of the fats thus occurs in the growing ovaries. In 

 the ovaries the amount of lecithin is very large, but the amount in the 

 testes is by no means trifling, and the constant occurrence of this sub- 

 stance seems to point to it as the first stage in the formation of nucleins. 



///. Proteids of Muscle, Genitalia, etc. 



Dr. Boyd's observations (p. 112) indicate that the albuminous 

 materials of the muscle may be divided into two classes : (1) Those 

 soluble in salt solution ; (2) those not soluble in salt solution. He 

 shows that globulin substances constitute nearly the whole of the soluble 

 proteids, and that proteoses and peptones are not present in any circum- 

 stances. He further shows that there is a small quantity of some 

 phosphorus-containing proteid either a nuclein or a pseudo-nuclein 

 among the soluble proteids. It is these soluble proteids which diminish 

 in fish in fresh water. When they are abundant, as in fish at the mouth 

 of the river, on boiling they may coagulate between the flakes of the 

 muscle and form with the fats the characteristic curd. 



Of the insoluble proteids part is composed of white fibrous tissue, 

 part of a phosphorus-containing proteid which may be called myostromin. 



Dr. Dunlop's results (p. 120) show more fully the extent to which 

 proteids accumulate in the muscles, and the rate at which they diminish 

 as the fish passes up the river. The first point of interest is that the 

 proteids do not disappear to anything like the same extent or at the 

 same rate as the fats. As already indicated, it is from the fats that the 

 energy for muscular work is chiefly procured. The second point of 

 interest is that the proteid surplus available for energy that is, the 

 proteid not used in building the ovaries is no greater in the upper water 

 water fish in October and November than in July and August. This 

 seems to indicate that quite early in the season while the ovaries are grow- 

 ing slowly, the proteids disappearing from the muscle are more than 

 sufficient to meet the requirements of these structures, while later in/ 

 the year, when the growth of the ovaries is going on more rapidly, all 

 the proteid disappearing from the muscle is transported to and used in 

 them. 



A further point of interest brought out is that in the male the 

 amount of muscle proteid disappearing from the muscles is so much more 

 than sufficient for the requirements of the growing testes that a very- 

 much larger surplus is available for muscular work in the male than in 

 the female. 



IV. Source of the Energy for Muscidcw Work, etc. (p. 139J. 

 The extent to which the fats and proteids lost from the muscles are- 

 used for the construction of the genitalia on the one hand, and 

 for the liberation of energy on the other, varies somewhat in males and 

 females. Taking the earlier months, to August, it has been shown that 

 in the female 12 per cent, of the fats and 23 per cent, of the proteids go- 



