BULLETIN OF THE BUSSEY INSTITUTION. 183 
strongly marked on referring to the amounts of nitrogen that were found 
in the shell and in the organic matter that was separated from the shell. 
If, for example, the whole of the loss by ignition be regarded as organic 
matter, and the highest proportion of nitrogen (0.129%) that was found in 
the dried shell be referred to this supposed organic matter (3.61%), it 
would appear that the organic matter of the shell contained only 34% of 
nitrogen; whereas the organic matter actually separated from the shell 
‘by dissolving the lime-salt in acid contained 6}% of nitrogen. Never- 
theless, it is not wholly improbable that a good part of the organic matter 
in the oyster-shell is soluble in dilute acids, and that the observed differ- 
ences between the ‘“‘ loss by ignition ’’ and the organic matter, separated 
by means of an acid, are to be explained in this sense. Schlossberger * 
did in fact long ago resort to this explanation. On noticing that the 
amount of loss, when oyster-shells were incinerated, was often a quarter 
larger than the amount of organic matters obtained by dissolving the 
lime-salt in an acid, and collecting the undissolved portion of the shell, 
he concluded that chlorhydric acid, even when very highly diluted, must 
dissolve a considerable proportion of the organic matter of the oyster- 
shell. 
It will be noticed that the percentage of nitrogen (6.37) found in the 
organic matter that was left when the oyster-shell was treated with an 
excess of dilute acid is remarkably like the amount (6.44¢,) that is con- 
tained in chitin. But this coincidence is to be regarded as accidental 
merely. Chitin, though abundant in the shells of lobsters and crabs, has 
never been found in sea-shells. Moreover, one of the most important 
steps in the preparation of chitin is to boil with strong potash-lye the crude 
organic matter that is left when the carbonate of lime of the lobster-shell 
has all been dissolved out by means of acids. The hot alkali dissolves 
(various ?) nitrogenized matters that were mixed with the chitin, and 
leaves the latter free. So, too, when the organic matter that is left by the 
action of acids upon sea-shells is boiled with potash-lye, a very considera- 
ble proportion of it dissolves, and conchiolin is left free. With regard to 
the special instance now under consideration, Schlossberger * insisted long 
ago that the organic matter of the oyster-shell, as left after the lime-salt 
has been removed by a weak acid, consists of at least two different sub- 
stances which may be roughly separated from one another by elutriation. 
One is a tough, brown, somewhat transparent, membrane, and the other 
consists of white or gray membranous flocks of very different structure 
from the brown matter. The gray flocks dissolve well-nigh completely 
on being boiled in potash-lye; and the brown membrane, which is very 
much more abundant than the gray flocculent matter, gives up 46%, of its 
weight when boiled with the potash. But the residue, insoluble in pot- 
ash, left after the boiling, was found to contain from 16 to 16.7% of nitro- 
gen; that is to say, very nearly the amount that is contained in conchiolin. 
* “ Annalen der Chemie und Pharmacie,” 1856, 98. 103. 
