358 THE FLUIDS OF THE EGG. 



on the other hand, we can gain little or no information from 

 elementary analyses as to the difference or identity of protein- 

 bodies. 



I found 1 3*93 2 of such casein in 100 parts of yolk-fluid (pre- 

 cipitated by acetic acid from a solution of hydrochlorate of 

 ammonia). The quantity of matter insoluble in the solution of 

 hydrochlorate of ammonia (the investing membranes) amounted 

 only to 0-45 9. 



The albumen of the yolk is contained in the fluid that is 

 obtained by washing the casein which is insoluble in pure water ; 

 on boiling, it coagulates in flakes a proof that nothing is con- 

 tained therein but an albuminate, since in all other properties it 

 resembles ordinary albumen, and is neither precipitated by acetic 

 acid, nor coagulated by rennet. Of albumen of this nature, 

 which is soluble in pure water, I found 2'841-g- in the fluid of the 

 yolk ; while of such as remained undissolved with the casein, and 

 was only quantitatively determined after the precipitation of the 

 casein by acetic acid, there was 0'892-g-. Prout found 17&, and 

 Gobley 15*76 of vitellin in the yolk ; this vitellin consisting of a 

 mixture of casein, albumen, and investing membranes. 



In addition to the above named protein- bodies, we find in the 

 yolk both of fishes' and birds' eggs, a number of substances 

 soluble in ether which are fats, or, at all events, on decomposition, 

 yield acid and neutral fats, and contain in solution two pigments. 

 The whole amount of these substances soluble in ether was found 

 by Prout to be 29 -, and by Gobley to be 30'468, while I found 

 on an average, as much as 31' 146$. Sulphur has not been 

 found in the yolk-fat either by Gobley or myself : neither the alco- 

 holic solution of the yolk-fat, nor the water in which the fat has 

 been warmed, reddens litmus. 



In the examination of these fats, the first substances to notice 

 are olein and margarin, whose quantity Gobley estimates at 

 2 J -304. 



It has been generally assumed the cholesterin is present in the 

 yolk, and Gobley has even determined it quantitively, and found 

 that it amounted to 0'438$. The evidences of its presence are, 

 however, not at all decisive, even though the fusing point of the 

 unsaponifiable fat obtained by Lecanu from egg-oil coincides with 

 that of cholesterin, being 145 C. At all events, I have never been 

 able to convince myself, by a measurement of the angles of the 

 crystals which have been assumed to be cholesterin, or by any 

 other means, that this lipoid was actually present : the crystalline 



