of the Salmon in Fresh Water. 143 



13. THE PHOSPHORUS COMPOUNDS OF THE MUSCLE 

 AND GENITALIA OF THE SALMON, AND 

 THEIR EXCHANGES. 



BY D. NOEL PATON, M.D. F.R.C.P. ED. 



Phosphorus forms an essential constituent of every living creature, 

 and in the higher animals it is very widely distributed in the different 

 tissues in various combinations. In the bones and other tissues it 

 occurs as inorganic phosphates, possibly in loose organic combination. 

 It also occurs as stored nutrient material in the yolk of the egg in at 

 least two forms (a) as pseiido-nucleins, substances yielding a proteid 

 and phosphoric acid when split, and (b) as lecithin in which a molecule 

 of the fatty acid radicle of a glycerine fat is replaced by phosphoric acid 

 linked to a peculiar nitrogenous base, cholin. Lastly, in protoplasm, 

 and more especially in the nucleus of the cells, it occurs in nnclein com- 

 pounds compounds in which a proteid is linked to nucleic acid a 

 substance which, on being broken down, yields phosphoric acid and 

 various nitrogenous bases such as xanthin. 



The most complex of these phosphorus compounds are the true nucleo- 

 proteids. It is these compounds which, in the nuclei of cells, play so 

 important a part in the various phenomena of living matter. 



That lecithin is a forerunner of these substances is shown by the 

 study of the disappearance of lecithin in the egg during incubation as 

 the embryo develops. 



Whether the pseudo-nucleins are also forerunners of these true 

 nucleins has, so far as I am aware, never been considered. The fact 

 that they exist in large quantities in the yolk of the egg would indicate 

 that in them the phosphorus is also stored for use in the construction 

 of nucleins, while the possible combination of their phosphorus in 

 thymic acid a derivative of nucleic acid seems a further indication of 

 their relations to the true nucleins. 



It would be difficult to find a more suitable object for the study of 

 some of the transformations of phosphorus than the salmon during its 

 prolonged fast, when its genitalia are being built up from its other 

 tissues. 



Miescher Ruesch does not deal fully with the question. He states (p. 

 1 83) that the ovarian fluid, which readily exudes from the ripe ovary when 

 broken down, contains no less than 20 per cent, of lecithin, besides a 

 nuclein the amount and characters of which he does not discuss. He 

 points out that this has "general interest because both these substances, 

 especially the last named, are contained only in very small amounts in 

 muscle. The formation of the ovarian fluid can thus only take place by 

 the muscle substance being taken up from the flesh and laid on in the 



