100 Dr. Prout on the Changes in the fixed Principles- [Feb. 



the purple or blue vegetables examined by that chemist. I col- 

 lected a number more of such purple flowers as are most com- 

 monly met with, and dipped them separately in concentrated 

 sulphuric acid. But instead of becoming blue, they were 

 uniformly changed to red, and formed red coloured solutions on 

 the addition of water. Future inquiries, therefore, must deter- 

 mine whether phenicin exists ready formed in nature either in 

 the blue or in the purple state. 



Alcohol modifies remarkably the action of sulphuric acid upon 

 indigo. A mixture of three parts of alcohol, of specific gravity 

 0*84, and two parts of acid, dissolves indigo without rendering 

 it yellow, and the solution may even be filtered through strong 

 paper. Probably a larger quantity of pure alcohol might be 

 employed. On the addition of water, the indigo is precipitated 

 without alteration ; and if common indigo has been used, resin 

 precipitates along with it. It may remain dissolved in this mix- 

 ture any length of time without conversion into phenicin. A 

 solution of phenicin in sulphuric acid may also be mixed with 

 alcohol without precipitation, and the acid is rendered incapable 



of converting it into cerulin. 



Article II. 



Some Experiments on the Changes which take place in the fixed 

 Principles of the Egg during Incubation. By William Prout, 

 MD. FRS * 



" In the year 1816," says Dr. Prout, u I was induced to com- 

 mence a series of experiments on the egg during incubation, 

 with the view of ascertaining the nature of the changes which 

 take place during that process. My inquiry was chiefly limited 

 to the fixed principles ; namely, the earthy and saline matters ; 

 but my attention was more particularly directed to the source 

 whence the earthy matter, constituting the skeleton of the chick, 

 was derived." 



" With these views, the egg was analyzed in its recent and 

 unaltered state, and at the end of the first, second, and third 

 weeks of incubation. My experiments were chiefly confined to 

 the eggs of the domestic fowl, but have been likewise partially 

 extended to those of the duck and turkey. The investigation 

 has been renewed, and the experiments repeated at various inter- 

 vals since the period above-mentioned ; but the difficulty of the 



* Abstracted from the Philosophical Transactions for 1822, Part II. 



