Chap. VI.] DIGESTION. 89 



enamel and dentine, but did not expect that it would succeed 

 with so hard a substance as enamel. Dr. Klein gave me 

 some thin transverse slices of the canine tooth of a dog; 

 small angular fragments of which were placed on four leaves ; 

 and these were examined each succeeding day at the same 

 hour. The results are, I think, worth giving in detail. 



Experiment 1. May Ist, fragment placed on leaf; 3rd, tentacles 

 but little inflected, so a little saliva was added; 6th, as the tenta- 

 cles were not strongly inflected, the fragment was transferred to 

 another lerff, which acted at first slowly, but by the 9th closely 

 embraced it. On the 11th this second leaf began to re-expand; the 

 fragment was manifestly softened, and Dr. Klein reports, " a great 

 deal of enamel and the greater part of the dentine decalcified." 



Experiment 2. May 1st, fragment placed on leaf; 2nd, tentacles 

 fairly well inflected, with much secretion on the disc, and remained 

 BO until the 7th, when the leaf re-expanded. The fragment was 

 now transferred to a fresh leaf, which next day (8th) was inflected 

 in the strongest manner, and thus remained until the 11th,. when it 

 re-expanded. Dr. Klein reports, " a great deal of enamel and the 

 greater part of the dentine decalcified." 



Experiment 3. May 1st, fragment moistened with saliva and 

 placed on a leaf, which remained well inflected until 5th, when it 

 re-expanded. The enamel was not at all, and the dentine only 

 slightly, softened. The fragment was now transferred to a fresh 

 leaf, which next morning (6th) was strongly inflected, and re- 

 mained so until the 11th. The enamel and dentine both now some- 

 what softened ; and Dr. Klein reports, " less than half the enamel, 

 but the greater part of the dentine decalcified." 



Experiment .'/. May 1st, a minute and thin bit of dentine, 

 moistened with saliva, was placed on a leaf , v.'hich was soon inflected, 

 and re-expanded on the 5th. The dentine had become as flexible as 

 thin paper. It was then transferred to a fresh leaf, which next 

 morning (6th) was strongly inflected, and reopened on the 10th. 

 The decalcified dentine was now so tender that it was torn into 

 shreds, merely by the force of the re-expanding tentacles. 



From these experiments it appears that enamel is at- 

 tacked by the secretion with more difficulty than dentine, as 

 might have been expected from its extreme hardness; and 

 both with more difficulty than ordinary bone. After the 

 process of dissolution has once commenced, it is carried on 

 with greater ease; this may bo inferred from the leaves, to 

 which the fragments were transferred, becoming in all four 

 cases strongly inflected in the course of a single day; where- 

 as the first set of leaves acted much less quickly and ener- 

 getically. The angles or projections of the fibrous basis of 



