PLANTAR SYSTEM. 437 



By chemical analysis horn has been found to consist of mem- 

 branous substance, having the properties of coagulated albumen, 

 and of some gelatine. The horns of some animals, the deer 

 species, from containing bone, become exceptions to this. Mr. 

 Hatchett burnt five hundred grains of ox's horn, and the resi- 

 duum proved only one and a half grain, not half of which was 

 pliosphate of lime. 



Shavings of hoof thrown into nitric acid become soft, and 

 speedily melt into a yellow mass, which in about eight hours 

 disappear in complete solution. 



The same thrown into sulphuric acid, turn black, in becoming 

 soft, and require thrice the time for their solution. Muriatic acid 

 also turns horn black, and corrodes it, but has so little effect 

 towards its solution, that after ten days a piece of hoof soaked in 

 it was found to have become only more brittle or rotten. Common 

 vinegar will turn horn dark-coloured, but does not appear to have 

 any power in impairing its texture, or, at least, in dissolving it. 

 Liquor potassai will not only turn it black, but will corrode the 

 horn of the hoof. Ammonia does not change its colour, but 

 slowly destroys its texture, rendering it brittle and rotten. 



INTERNAL PARTS OF THE FOOT. 



THE internal, sensitive, organic parts of the foot, comprise 

 the hones, ligaments, tendons, coronaty substance, cartilages, sen- 

 sitive lamina, sensitive sole, and sensitive fi'og. 



THE BONES entering into the composition of the foot are 

 the coffin and navicular bones : to which may be added (as form- 

 ing part of the coffin-joint, and consequently having intimate re- 

 lation to them), the coronet bone. Their descriptions will be 

 found given at pages 57, 58, 59, and 60. 



THE LIGAMENTS have likewise been already described at 

 page 75, in giving the particulars of the coffin-joint. 



THE TENDONS immediately connected with the foot are 

 those of the extensor pedis and the Jiexor pedis perj'oraiis : the 

 former being inserted into the posterior concavity of the coffin- 

 bone ; the latter into its coronal process, as described at pages 

 140 and 144. 



The Coronary Substance, 



A less inappropriate name for the part commonly called the 

 coronan/ ligament*. 



* Averse as I am to changing- or altering names, nothing less than a 

 palpable contradiction, in regard both to slrncdtre and fttnction, would have 

 induced me to do so in the present instance. 



