382 Mr. Hatchett's Experiments on Zoophytes, 



arrangement) as the principal cause of those degrees of flexi- 

 bility, of elasticity, and of putrescibility, so various in the 

 different parts of animals.* 



But, when gelatin has been separated from the different 

 substances, either by repeated boiling with water, or by being 

 steeped in dilute acids, a more insoluble substance remains, 

 of a very different nature, which I shall now proceed to 

 examine. 



When a bone or piece of ivory has, by long boiling in 



* As gelatin, according to its proportion and quality, appears to produce consider- 

 able effects on the parts of animals in which it is present ; and, as the gelatin in animal 

 bodies is, in all probability, liable to be changed and modified by morbid causes, it is 

 much to be wished, that gentlemen of the medical profession would ascertain, by expe- 

 riments, how far the tonic properties of barks depend on the tanning principle. 



Mr. Biggin has proved, (Phil. Trans, for 1799. P- 2 59 ) tnat w iU° vv bark, and 

 especially that of the Huntingdon or Leicester willow, contains the tanning matter in 

 a considerable quantity ; and that the latter, in this respect, even equals, or rather ex- 

 ceeds, that of oak. 



My friend, the Rev. Thomas Rackett, Rector of Spetisbury and Charlton, in 

 Dorsetshire, has employed, in those parishes, the bark of the common willow with 

 great success, as a tonic and febrifuge. Moreover, Mr. Westring, of Norvkoping, 

 has observed, {Annates de Cbimie. Tom. XXXII. p. 179) that those species of Cin- 

 chona which contain the tanning principle in the greatest quantity, are the most 

 efficacious in fevers ; and that the Cinchona fiorihunda, which contains scarcely any 

 tanning matter, is destitute of the abovementioned beneficial effects. Mr. Westring 

 therefore, with great apparent reason, believes, that the relative effects produced by 

 the different species of Cinchona, when employed in medicine, are in proportion to 

 their tanning power, or the quantity of tanning principle contained in them. 



If any one should be induced to make experiments on the tonic effects of the 

 tanning principle, it is to be hoped that some attention would also be paid to the 

 medicinal properties of nitro-muriate of tin, of which, at present, I believe little or 

 nothing is known. 



