Chap. VI.] DIGESTION. 79 



lay the process; for, after 48 hrs., the cubes were completely dis- 

 solved on all three leaves. On the third day the leaves began to 

 re-expand, and on the fourth day all the fluid was absorbed. 



Experiment 7. Small cubes of albumen were put on two leaves, 

 and minute drops of hydrochloric acid, of the strength of one part 

 to 437 of water, were added two or three times. This did not in 

 the least delay, but seemed rather to hasten, the process of diges- 

 tion; for every trace of the albumen disappeared in 24 hrs. 30 m. 

 After three days the leaves partially re-expanded, and by this time 

 almost all the viscid fluid on their discs was absorbed. It is al- 

 most superfluous to state that cubes of albumen of the same 

 size as those above used, left for seven days in a little hydro- 

 chloric acid of the above strength, retained all their angles as per- 

 fect as ever. 



Experiment 8. Cubes of albumen (of ^ of an inch, or 1.27 mm.) 

 were placed on five leaves, and minute drops of a solution of one 

 part of carbonate of soda to 437 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 I ascertained that each was equal to about 

 I'i,^ of a minim (.0059 c.c), so that each contained only -^^ of a 

 grain (.0135 mg.) of the alkali. This was not sufficient, for after 

 46 hrs. all five cubes were dissolved. 



Experiment 9. The las 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 dissolved, 

 whilst the fourth was converted into a minute sphere, surrounded 

 by transparent fluid ; and this sphere next day disappeared. 



Experiment 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 Tj^ifff of 

 a grain (.0539 mg.) of either salt. Two cubes of albumen (each 

 about ^ 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 neu- 

 tralised. 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 with 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 was used as the solutions of the alkalies were 



