64 On the Alteration which Air and Water produce on Meat: 
days the oxygen was changed into carbonic acid; the in- 
terior of the cylinder was infected with a putrid smell; the 
beef that had been boiled gave once more an abundant pre= 
cipitation with tannin: the ebullition was repeated until the 
water was no longer disturbed by the tannin: the beef had 
then almost entirely lost its smell, and it was put again into 
the apparatus. 
The operation was repeated several times, when the fol- 
lowing were the results :— 
The alteration of the atmospheric air and the disengage- 
ment of the putrid smell gradually slackened: the quantity 
of gelatine formed became progressively smaller: the water 
upon which the vessel rested gave only feeble indications 
of ammonia. When I finished the operation there was no 
longer any putrid smeli; but a smell similar to that of 
cheese, and in fact the animal substance which now pre- 
served scarcely any fibrous appearance, had not only the 
smell, but precisely the taste of old cheese. 
I distilled, separately, an equal weight of beef and of 
Gruyere cheese, making use of two bell-glasses, each of 
which communicated with a tube inserted in water: the 
operation was conducted so as to decompose, as much as 
possible, the two substances, and to retain all the ammonia 
which was set free: I compared the quantities of ammonia; 
that which was furnished by the cheese was to that of the 
beef nearly in‘the ratio of }9 to 24: hence it appears that 
it is one of the distinctive characters of the caseous sub- 
stance to contain less azote than meat does. 
If we may be permitted to draw any inferences from the 
foregoing imperfect experiments, we may conclude : 
Ist. That the gelatine which we may obtain from an 
animal substance is not completely formed in it ; but that 
when this substance has been exhausted by water, it may 
be once more formed by the action of the air, the oxygen 
of which is combined with the carbon, while a portion of 
substance formerly solid becomes gelatinous, as a solid ve- 
getable part becomes soluble by the action of the air. 
We must, however, remark, that the property of precipi- 
tating with tannin belongs to substances which have ver 
different properties in other respects: I found that the de- 
coction of Gruyere cheese formed an abundant precipitate 
with tannin. ; 
ad. That azote enters into the composition of the putrid 
gas, forming without doubt with hydrogen a combination 
of an equilibrium less stable than ammonia, or rather an 
;ntermediary combination; but when its proportion is di- 
minished 
