294 
PHYSIOLOGY. 
BOOK II. 
“ 3. The second (1. b.) by short boiling in the caustic alkali 
is converted into starch, carbonic acid being evolved (granting 
that starch is the only substance upon which iodine acts so 
characteristically ) . 
4. The third (1. c.) by boiling in caustic potash is con- 
verted into a peculiar, as yet unknown (?), vegetable prin- 
ciple, which is coloured orange yellow by iodine. Whether 
in this case carbonic acid be also formed, I will not take 
upon myself to decide ; at least in Experiment VIII., on the 
addition of sulphuric acid, I did not observe any efterves- 
cence. Moreover, this orange colour is as distant as heaven 
from earth, from the colour produced by adding iodine to 
vegetable mucus. 
Whether the carbonic acid be formed at the expense of 
the carbon of the vegetable substance uniting with the 
oxygen of the air, or by the decomposition of the water, re- 
mains still to be investigated ; as, likewise, to discover whether 
by longer boiling, it could take up more carbon, and become 
converted into oxalic acid. 
“ The most interesting result is, however, without doubt, 
that, by the action of the caustic potash, one portion of vege- 
table matter becomes, by a retrograde metamorphosis, as it 
were, again converted into starch ; a discovery, the extension 
of which gives promise of most interesting results for organic 
chemistry.’^ 
M. Payen selected with the utmost care the nascent tissue 
of the ovules of the Almond, Apple, and Sunflower ; the half- 
formed tissue of the Cucumber; the sap of the same plant; the 
two months’ old pith of the Elder ; the pith of ^schynomene 
paludosa ; the hairs of Cotton ; and the new tissue of spon- 
gioles. They gave him the following results : — 
Almond. 
Apple. 
Sunflower. 
Sap of 
Cucumber. 
Tissue of 
Cucumber. 
Elder. 
6 
'og 
O S 
S c 
>-g 
Average of 
Cotton. 
Spongioles. 
Carbon 
43-57 
44-7 
44-1 
43-9 
43-8 
43-37 
43-31 
44-67 
43- 
Hydrogen - 
6-11 
6- 
6-2 
6-22 ’ 
6-11 
6-04 
6-9 
5-68 
6-18 
Oxygen - 
50-32 
49-3 
49-7 
49-88 
50-1 
50-59 
50-1 
49-3 
50-82 
But when he came to analyse wood in which a deposit had 
