INTERNAL STRUCTURE OF PLANTS. 
15 
behayed in the same manner as cotton. It was difficult to 
separate firwood from all foreign substances ; the membrane, 
however, after this had been accomplished, exhibited the usual 
composition. The membrane of Cetraria islandica, cleansed 
by water, alcohol, ammonia, acetic acid, and ether, still 
assumed a blue colour on the application of iodine ; and the 
jelly of tliis lichen contained hydrate of starch and inulin. 
This last substance is resolved into a sugar by acetic acid, 
which is dissolved in water, and also in alcohol. On dis- 
solving inulin in boiling water, it is separated, when left to 
cool, into small, white, and transparent globules, like starch 
globules ; they do not, however, assume a blue colour on the 
application of iodine. The albumen of dates may be en- 
tirely dissolved by potass, in the same way as the membrane 
of Cetraria islandica. It was more difficult to remove depo- 
sited substances from the Confervce and CJiara hispida; pre- 
caution was necessary with the Fungi ; but a membrane of the 
usual composition remained in all these cases. The author de- 
scribes different forms of starch granules in the Cliara; but 
they were not different in a chemical point of view. The tender 
membrane in the orange coloured organs of the Cliara exhi- 
bited the usual composition of vegetable membrane ; the sub- 
stances contained in it, however, were very nitrogenous. The 
author expresses the opinion, that all nitrogenous materials 
in plants, are only deposited, whilst they penetrate into the 
membranes themselves of animals. He obtained the prepared 
gut of a sheep, from a manufacturer of stringed instruments, 
treated it with water, acetic acid, and potass, of which the 
two latter had a peculiar dissolving effect, analyzed the re- 
mainder, and found a nitrogenous quaternary compound. This 
residue had also, in other respects, the general qualities of 
animal membrane ; it dissolved in acetic acid and diluted 
muriatic acid, which is not the case with vegetable membrane. 
The author compares the distinguishing marks of pure vege- 
table and animal membrane ; and, besides the one enumerated, 
I may add, that the latter is dissolved by the diluted solutions 
of potass and soda, and ammonia, but not the former. Fur- 
ther, that tannic acid, alum, and corrosive sublimate, do not 
407 
