THE YOLK. 355 



essential difference being that the fat may be completely extracted 

 from the yolk, even without the application of acetic acid, potash, 

 hydrochlorate of ammonia, &c., although this may certainly be more 

 rapidly effected by the application of hydrochlorate of ammonia 

 or similar means. When we examine the yolk under the micro- 

 scope, after the fat has been as far as possible removed by ether, 

 we find that the minute granules are no longer scattered, but 

 conglomerated into larger masses or aggregations, which are in a 

 great measure dissolved by hydrochlorate of ammonia, acetic acid, 

 and caustic potash, leaving only very fine, scarcely perceptible 

 granules and flakes, which impart to the fluid a general opalescent 

 or whey-like appearance. 



I made numerous experiments, eight or ten years ago, on the 

 constitution of the fluids of the egg, and the changes they undergo 

 during the period of incubation, but deferred the publication of 

 my observations, because the state of science at that time did not 

 furnish the means of replying to the questions which I had pro- 

 pounded. I have unfortunately been prevented from repeating 

 these experiments, which I the more regret, as the early observa- 

 tions of a mere beginner, conducted by means of the imperfect 

 methods then in use, are but ill adapted to aid in criticising 

 Gobley's recent experiments, which undoubtedly call for a rigid 

 scrutiny in respect to several special points. 



We are unable to determine the constitution of the spherical, 

 cell-like fat-corpuscles of the yolk, as we have as yet neither the 

 mechanical or chemical means necessary for the complete separa- 

 tion of the intercellular fluid. 



They contain, as far as we are at present able to determine, 

 scarcely anything but fat ; which, however, is intermixed with the 

 phosphorised matters of the yolk-fat. Such, at all events, seems 

 to be the case, if we may judge by the following experiment. On 

 repeatedly shaking the yolk with ether, we find that the portions 

 of fat first extracted contain little or no substance yielding phos- 

 phoric acid, while those portions which have been the latest 

 extracted by shaking the yolk with ether yield, on incineration, a 

 very large quantity of the superphosphates of the alkalies and of 

 lime. This difference in the quantity of phosphorus contained in 

 the different portions of the fat is not observable when the yolk has 

 been previously treated with hydrochlorate of ammonia, acetic 

 acid, or potash. If the investing membranes of the yolk-globules 

 were completely impervious to ether, this substance, when pure, 

 would only extract fat free from phosphorus, whilst hydrochlorate 



