380 Mr. Hatchett's Experiments on Zoophytes, 



Gelatin, according to its quantity and quality, has a powerful 

 influence on some of the physical and chemical properties of 

 the bodies in which it is present ; by these properties, I mean 

 flexibility, elasticity, and putrescibility. 



So much has been said already, in various parts of this paper, 

 tending to prove how much the degrees of flexibility and elas- 

 ticity, in various animal substances, depend on their gelatinous 

 part, that little need be added ; and, when it is considered, that 

 bodies such as muscular fibre, membrane, sponge, hair, and 

 cuticle, being deprived of gelatin, and dried in the air, become 

 rigid and brittle, no doubt can be entertained but that this 

 arises from the loss of the gelatinous substance; and, as an 

 additional proof, when bodies such as nail, feather, quill, and 

 tortoise-shell (which contain little or no gelatin) are long 

 boiled, and then dried in the air, like the former, they are 

 found to have suffered scarcely any alteration in their respec- 

 tive degrees of flexibility and elasticity. 



As to putrefaction, it is obvious to every one, that certain parts 

 of animals are much more susceptible of it than others ; and 

 that, when the carcase of an animal begins to putrefy, the most 

 humid and flexible parts are always first affected. 



Thus, the viscera, muscles, and cutis, soon suffer a change ; 

 while hair, feather, scale, horn, hoof, and nail, remain unchanged, 

 ages after the former have been decomposed ; and this is evi- 

 dently caused by the gelatin and moisture, which are combined 

 in the former, and not in the latter, at least in any notable 

 quantity. I have already mentioned the progressive and com- 

 parative effects of boiling water, and of dilute nitric acid, on the 

 skin of the ox ; and I have shewed, that while the cutis was 

 completely dissolved, the hair remained untouched. These effects 



