238 Dr THOMSON'S Experiments on the 



soever concentrated, possesses no agglutinating properties like 

 those of a solution of gum or sugar. When it was evaporated 

 to dryness, a shining brown coloured matter remained, having 

 an acrid taste, and somewhat altered by the heat. This sub- 

 stance bore a closer resemblance to ulmin than to any other ve- 

 getable principle, though its properties were different in some 

 respects. Thus, its solubility in water was promoted by acids, 

 which is not the case with ulmin. This brown substance is so 

 scanty, that I never could procure more of it than one grain. 

 It was therefore impossible to examine it minutely, or to deter- 

 mine its exact nature. 



The white waxy substance left by the water being repeatedly 

 digested in hot alcohol, was all dissolved, with the exception of a 

 few pink-coloured flocks, which, after being thoroughly washed in 

 hot alcohol, and then left to dry in the open air, assumed a dark 

 brown colour. These flocks were tasteless, and insoluble both 

 in water and alcohol. When digested in nitric acid, they swelled 

 up, and assumed the same appearance as a piece of cork would 

 have done, if placed in similar circumstances. By continuing 

 the digestion, a solution was obtained. Being evaporated to 

 dryness, the yellow coloured residue was bitter, and scarcely so- 

 luble in water. It was three times successively dissolved and di- 

 gested in nitric acid ; but no crystals of oxalic acid were formed. 



In muriatic acid, this substance became soft and spongy like 

 cork, but did not dissolve. In sulphuric acid, it gradually dis- 

 solved, blackening the acid, and, when water was added, a black 

 deposit gradually subsided. In caustic potash ley, it became 

 soft, and almost gelatinous, but did not dissolve. 



I was more minute in my examination of this substance, be- 

 cause it seems to be what MM. BOUSSINGAULT and MARIANO DE 

 RIVERO have distinguished by the name of fibrin. It exists in 

 the cow-tree milk only in small quantity. It approaches much 

 more nearly to cork than to any thing else. None of its charac- 



