July 21, 1898] 



NATURE 



281 



The method employed was as follows. From the constant 

 stream of salmon setting from sea to river specimen fish were 

 taken (i) from the estuaries just as the fish were leaving the 

 sea, and (2) from the upper reaches of the river. The rivers 

 selected were the Spey, Dee and Helmsdale. Fish were taken 

 from these stations at three periods : (i) in May and June ; (2) 

 in July and August ; (3) in October and November. 



By comparison of the fish from the upper waters with those 

 just leaving the sea the nature and extent of the changes during 

 the passage of the fish up the rivers were determined. The 

 method may be compared to that of taking samples of the water 

 of a river from two points in order to determine the changes 

 Ijetween these points. 



In the course of these investigations results obtained from 

 salmon of very different sizes had to be compared, and therefore 

 all weighings, &c. , were expressed in terms of a fish of uniform 

 length — the standard fish. The length selected was 100 cm. 



The number of fish examined was 104, a number small as 

 compared with the myriads of fish which ascend the rivers. It 

 was considered necessary to investigate how far these fish were 

 fair average specimens of their classes. Mr. Archer's extensive 

 series of measurements and weighings of salmon from various 

 stations enabled him to ascertain that the female fish examined 

 by us were really average specimens, but that the small number 

 of male fish with which we had to deal were not so typical. 

 It is from observations on female fish that our conclusions are 

 drawn. 



The first question dealt with was the evidence as to whether 

 salmon feed in fresh water. Dr. Gulland shows that the 

 salmon coming from the sea early in the summer has the stomach 

 lined with a perfectly developed mucous membrane, while in the 

 intestine the mucous membrane is somewhat degenerated. In 

 fish taken from the upper waters the mucous membrane of 

 stomach and intestine are intensely degenerated. In kelts — 

 spawned fish passing back to the sea — there is a regeneration of 

 the mucous membrane. 



Dr. Gillespie has investigated the activity of the digestive 

 secretions by preparing in the usual manner glycerin extracts of 

 the mucous membrane of the stomach and intestine. He finds 

 in every case a very low digestive power. From this he con- 

 cludes that the fish even when approaching to the river mouth 

 have practically ceased to feed. 



His further studies of the bacteriology of the alimentary canal 

 show that, while in all situations,'as might have been expected, 

 the number of bacteria varies directly with the temperature of 

 the water, in fish from the upper water there is usually a larger 

 number of bacteria, and more especially a larger number of 

 putrefactive bacteria than in fish from the estuaries. From this 

 he concludes that the secretion of acid must be in abeyance in 

 the former. 



These investigations, taken with the evidence adduced by 

 Miescher, seem to leave no doubt that the salmon does not 

 digest and tise food during its sojourn in fresh water. 



It is because of this prolonged fast, and because of the 

 important changes going on in the fish during the fast, that 

 so interesting a physiological study in metabolism is afforded. 

 An opportunity is offered of investigating the manner in which 

 materials are stored in the animal body, the extent to which 

 they may be transferred from one organ to another, the nature 

 of some of the chemical changes they undergo, and the extent 

 to which the various stored materials are utilised as a source 

 of energy. 



Evidence is adduced to show that the fish taken in the upper 

 waters in May and June may have entered the river earlier in the 

 year, and it is therefore not considered fair to compare them 

 with the estuary fish of that period. On the other hand, there 

 is evidence that the fish leaving the sea from May to August go 

 to the upper waters, and hence the upper water fish of July and 

 .\ugust are compared with the estuary fish of May to August. 

 Evidence is also presented to show that the fish leaving the sea 

 in October and November do not pass to the upper reaches 

 tluring these months. Hence the upper water fish of October 

 and November are to be compjared with the estuary fish of May 

 to August. 



Adopting this method of comparison, the following results 

 have been obtained. 



Solids and Water of Muscle, Ovaries, &^c. — It is shown that 

 (luring the sojourn of the fish in fresh water there is a steady 

 loss of solids from the muscles and a steady gain of solids by the 

 genitalia, and that the gain of solids by the genitalia is small 



NO. 1499, VOL. 58] 



compared with the loss of solids from the muscle, that in fact 

 the greater part of the solids lost from the muscles are used for 

 some other purpose than the building up of the genitalia. 



Fats of Muscle, Ovaries, S^c. — Nothing is more extraordinary 

 than the enormous accumulation of fats which takes place in the 

 muscle of the salmon during its visit to the sea. Not only is 

 the tissue between the individual fibres loaded with fat, but, as 

 shown by Mr. Mahalanobis, an intrafibrous and interfibrillar 

 accumulation of fat occurs. In the river, as the season advances, 

 this accumulated fat steadily disappears from the muscle. There 

 is no reason to suppose that anything of the nature of a de- 

 generation 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, while the amount in the testes is by no 

 means trifling, and the constant occurrence of this substance 

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



Proteids of Muscle, Ovaries, Ssfc. — Dr. Boyd's observations 

 indicate that the albuminous materials of the muscle may be 

 divided into two classes : ( i ) those soluble in salt solution 'r 

 (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 show more fully the extent to which pro- 

 teids 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. 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 fish in October and November than iiv 

 July and August. This seems to indicate that quite early in the 

 season, while the ovaries are growing slowly, the proteids dis- 

 appearing 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. 



Phosphorus of Muscle, Ovaries, &'c. — It is shown that in the 

 female fish only just enough phosphorus is accumulated in the 

 muscle to supply the wants of the growing ovaries, while ir> 

 the male the accumulation is superabundant. In this connec- 

 tion it is further pointed out that in the male the enormous 

 growth of the bony jaw may use up a further amount of phos- 

 phorus. Whether in the female any phosphorus required for 

 the ovaries in excess of that stored in the muscle is procured 

 from the bones, these observations do not indicate. 



The phosphorus is stored in the muscle chiefly as phosphates, 

 and to a somewhat smaller extent as lecithin. The amount of 

 lecithin in the muscle is not nearly sufficient to yield the lecithin 

 of the ovaries. In the ovaries the phosphorus is largely ir» 

 the form of ichthulin, a pseudo-nuclein, so the phosphorus from 

 the phosphates of the muscles must undergo profound changes 

 in the growing ovaries, and being synthesised with organic 

 bodies be built into these compounds. That these compounds 

 are the forerunners of the still more complex nucleins of the 

 embryo is indicated. In the male the transference of the 

 phosphates of the muscle into these higher nuclein compounds 

 is even more direct, and the occurrence of lecithin in consider- 

 able amount in the growing testes seems to point to this sub- 

 stance as the first step in the synthesis of inorganic phosphates 

 to nucleic acid. 



Iron of Muscle and Ovaries.— Tir. Clreig has shown that the 

 ichthulin of the ovaries contains iron, and the amount of iron in 

 the ovaries thus increases as the organs grow. Whence is this 



