On the Composition of the Muscles in the Animal Series. 1 1 



compact body, with a strong taste, generally difficult to digest, 

 like the mackerel, - herring, trout, and, most of all, salmon, have a 

 large quantity. It is this phosphuretted substance which, by de- 

 composing incompletely through the action of heat, gives to 

 broiled fish its characteristic smell. 



While studying this substance in the muscles of fish, we have 

 been naturally led to examine the red matter which colors the 

 muscles of salmon, that which, in trout and some other fish, pro- 

 duces the ' saumonage.' This remarkable change of color is partly 

 dependent on the phenomenon of reproduction. The salmon, for 

 instance, is red-skinned all the year, but its muscles become per- 

 ceptibly paler at the time of spawning. This discoloration is 

 still more distinct in trout, for when they spawn the skin becomes 

 quite white. While the spawning does not occur at the same 

 time, the female 1 salmons ' itself a deeper red, and keeps this 

 color longer than the male ; and often in the same stream there are 

 taken white trout and salmon trout. This shows too that the 

 salmon trout is not the mongrel of the trout and salmon ; besides, 

 the fecundation of one of these fish by the other is out of 

 the question since the salmon spawns in July and rarely in Au- 

 gust, while the trout spawns in December. 



The coloring matter of the muscles of a salmon attracted the 

 attention of Sir Humphrey Davy ; in the work by this famous 

 chemist, entitled Salmonia, it is said that the skin of a salmon 

 can be discolored by ether. But even till now, this coloring 

 matter has not been isolated. It is this which we attempt to 

 accomplish. From our researches, we find this coloring matter to 

 be of a fatty nature, presenting the characteristics of a weak acid, 

 which we call salmonic acid, and that it dissolves in a neutral 

 oil. In order to isolate salmonic acid, we used the following 

 means : the red oil which is easily got from the muscles of a sal- 

 mon by a press, was agitated cold with alcohol feebly ammoni- 

 ated ; the oil then becomes colorless, and the alcohol takes the 

 coloring matter, which is separated by decomposing the ammoni- 

 acal salt with an acid. The acid thus obtained is viscous, red, and 

 presents all the characteristics of a fatty acid ; it is the same in 

 the salmon-trout as in the muscles of a salmon. We have found 

 it in considerable quantity and mixed with oleophosphoric acid 

 in the eggs of salmon, which partly accounts for the discolora- 

 tion and loss of smell in the flesh of a salmon when it la}^s. 

 The female of the Salmo hamatus FaZ., does not afford as much 

 acid, either salmonic or oleophosphoric, as the common sal- 

 mon (Salmo salmo Vol.) : the muscles of fish show therefore in 

 species most nearly allied appreciable differences in their compo- 

 sition. 



It was of interest to compare the muscles of Crustacea with 

 those of fish. In order to work at the muscular flesh of the for- 



