Cuar. VI. DIGESTION. 95 
cubes of albumen of the same size as those above used, left for 
seven days ina little hydrochloric acid of the above strength, 
retained all their angles as perfect as ever. 
Experiment 8.—Cubes of albumen (of 4 of an inch, or 2°54 
mm.) were placed on five leaves, and minute drops of a solu- 
tion of one part of carbonate of soda to 487 of water were added 
at intervals to three of them, and drops of carbonate of potash 
of the same strength to the other two. The drops were given 
on the head of a rather large pin, and | ascertained that 
each was equal to about ~, of a minim (-0059 ml.), so that _ 
cach contained only gds5 of a grain (0185 mg.) of the alkali. 
This was not sufficient, for after 46 hrs. all five cubes were 
dissolved. yi 
Eaperiment 9.—The last experiment was repeated on four 
leaves, with this difference, that drops of the same solution of 
carbonate of soda were added rather oftener, as often as the 
secretion became acid, so that it was much more effectually 
neutralised. And now after 24 hrs. the angles of three of 
the cubes were not in the least rounded, those of the fourth 
being so in a very slight degree. Drops of extremely weak 
hydrochloric acid (viz. one part to 847 of water) were then , 
added, just enough to neutralise the alkali which was still 
present; and now digestion immediately recommenced, so that 
after 23 hrs. 30 m. three of the cubes were completely dis- 
solved, whilst the fourth was converted into a minute sphere, 
surrounded by transparent fluid; and this sphere next day 
disappeared. 
Kaperiment 10.—Stronger solutions of carbonate of soda and 
of potash were next used, viz. one part to 109 of water; and as 
the same-sized drops were given as before, each drop contained 
robo Of a grain (0539 mg.) of either salt. Two cubes of albu- 
men (each about 2, of an inch, or ‘635 mm.) were placed on the 
same leaf, and two on another. Each leaf received, as soon as 
the secretion became slightly acid (and this occurred four times 
within 24 hrs.), drops either of the soda or potash, and the acid 
was thus effectually neutralised. The experiment now succeeded 
perfectly, for after 22 hrs. the angles of the cubes were as sharp 
as they were at first, and we know from experiment 5 that such 
small cubes would have been completely rounded within this 
time by the secretion in its natural state. Some of the fluid was 
now removed witb blotting-paper from the discs of the leaves, 
and minute drops of hydrochloric acid of the strength of one 
part to 200 of water was added. Acid of this greater strength 
‘vas used as the solutions of the alkalies were stronger. The 
