of the Salmon in Fresh Water. 93- 



8. CHANGES IN THE FATS OF MUSCLE, GENITALIA, 

 AND OTHER ORGANS OF THE SALMON IN FRESH 

 WATER, 



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



Throughout the animal kingdom the material required for the 

 evolution of energy is to a large extent stored in the body as fats. As 

 is well known, the combustion of one gramme of fats liberates about 

 twice as much energy as the combustion of a corresponding amount of 

 proteids or carbohydrates. In the salmon the ova are largely composed 

 of an oily fluid very rich in fats, and hence for the growth of the 

 ovaries a large store of fats in the body is necessary. 



In this section we have to consider where and how this fat is stored 

 and to what extent it is used as a source of energy and to what extent 

 for the growth of the genitalia. 



METHODS. 



A portion of the organ usually about 30 grins. was preserved 

 in spirit until it was analysed. The spirit was then poured into an 

 evaporating basin and the organ finely powdered in a mortar, added to 

 the spirit, and slowly dried over a water bath. When it had not 

 powdered easily at first, it was again powdered after drying. The 

 muscle readily broke up into very fine small fibrils, while the ovaries 

 and livers were readily reduced to a uniform powder. The powder 

 was placed in a filter paper, the mortar and basin being carefully 

 washed with ether and the ether added to the powder, and was then 

 extracted in a Soxhlet apparatus for two days. If by the end of this 

 time the ether was not absolutely colourless, the process was continued 

 until it became colourless. The ether was distilled off and the fat dried 

 at 100 C. and weighed. By the preliminary heating with alcohol the 

 extraction of lecithin was facilitated. 



This method was used in preference to the more recent procedure of 

 Dormeyer (Pfliiger's Arch. Bd. 65, p. 90), because the residue after 

 extraction of fats was required for the estimation of proteids, phos- 

 phorus, and iron. To have put aside separate specimens for the 

 analysis of each of these would have increased the accumulation of 

 material to an unmanageable extent. As it was, no less than six or 

 seven bottles of material were put aside for each fish. 



In face of Dormeyer's severe strictures upon Soxhlet's method it was 

 necessary to test it carefully against the method devised by the former. 



Dormeyer found that with horse flesh Soxhlet's method of extraction 

 failed to remove a very considerable portion of the fats, and he recom- 

 mends that after an initial extraction bv Soxhlet's method the residue 



