and Observations on the component Parts of Membrane. 387 



enumerated, convinced me moreover, by the similarity of re- 

 sults, that they essentially consisted of one and the same 

 substance, modified in texture by the degrees of organic arrange- 

 ment, and by the occasional presence, and different proportion 

 and quality, of gelatin. 



But the difference in chemical properties shewed, that this 

 last mentioned substance (I mean gelatin) was quite distinct 

 from that which is now under examination; and, from the 

 resemblance of certain effects observed when quill and tortoise- 

 shell were compared with inspissated albumen, by being long 

 digested in boiling water, I was induced to make a series of 

 comparative experiments upon albumen, similar in every respect 

 to those which have been so lately described, of which the fol- 

 lowing are the results. 



1 . By distillation, the coagulated dry semi-transparent albu- 

 men, afforded products exactly similar to those obtained from 

 tortoise-shell, and the other substances which have just been 

 examined. ; . ■; 



2. A spongy coal remained, of very difficult incineration ; as 

 towards the end of the process it appeared vitrified, and glazed 

 with a melted saline coat, which was, however, easily dissolved 

 by water. 



The residuum was again exposed to a long continued red 

 heat, and again treated with water, till, at length,; a few scarcely 

 visible particles remained ; which, as far as Such a small quantity 

 would permit to be ascertained, proved to be phosphate of lime. 



The portion dissolved by water (which was by much- the 

 most considerable) consisted .principally of carbonate, mixed 

 with a small quantity of phosphate of soda. 



3. When steeped in dilute nitric acid, it was not soon affected ; 



