OF THE ANIMAL FRAME. 



117 



of the skin pour forth a copious efflux or sweat of calcareous matter all 

 over the body, the more liquid parts of which are as rapidly drunk up by 

 the absorbent vessels, so that a new calcareous membrane is very soon 

 produced, which as speedily hardens into a new calcareous crust, and the 

 entire process is completed m about a fortnight. This genus, also, in 

 many of its species, is capable of reproducing an entire limb, with the 

 whole of its calcareous casing, whenever deprived oi* it by accident or 

 disease, or it voluntarily throws it off, as 1 have already observed it is ca- 

 pable of doing, to extricate itself from being seized hold of : though the 

 new Hmb is seldom so large or powerful as the original. So, in other ani~ 

 mals we sometimes find a large and preternatural secretion of calcareous 

 matter, in consequence of a diseased habit of particular organs, or of the 

 system generally. The human kidneys are too often subject to a morbid 

 affection of this kind, whence a frequent necessity for one of the most 

 painful operations in surgery. The chalk-stones, as they are erroneously 

 called, that are often produced in protracted fits of gout and rheumatism^ 

 are rather lithate of soda than any compound of lime ; but instances are 

 not wanting in which one of the lungs has been found converted into an 

 entire quarry of limestone. 



In the Transactions of the Royal Society there are several cases related 

 of young persons wlio, in consequence of a morbid habit, threw out a 

 variety of calcareous excrescences, either over the hands or feet, or over 

 the whole body and about four years since, a Leicestershire heifer was 

 exhibited for a show in this metropolis, the head and neck of which were 

 completely imbedded in horny excrescences of this kind, and the back 

 and hrnbs profusely sprinkled over with them : some of the horns, and es- 

 pecially those about the dew-lap, were as long and as large as the natural 

 horns of the forehead, but they were much more calcareous and brittle^ 

 A calcareous scurf, moreover, was secreted over every part of the skin, 

 which, whenever the skin was scratched or bitten, united with the fluid that 

 ooz6d forth, ramified, and divaricated into masses of small roses. At the 

 request of the proprietor I took an account of this extraordinary animal, 

 and have since communicated it to the Royal Society. In all other re- 

 spects it was in good health ; its size was proportionate to its age, and its 

 appetite enabled it to digest foods of every kind equally ; and though, in 

 consequence of this, its diet had been frequently varied, the propensity to 

 a secretion of calcareous matter continued the same under every change. 



It appears, therefore, very doubtful whether the animal economy be not 

 at times capable of generating lime, as well as gelatine or albumen, out of 

 the different materials introduced into the stomach in the form of food. 

 Vauquelin endeavoured to decide the question by a variety of experiments 

 upon the nature of the egg-shells of a sitting hen, and an examination into 

 the proportion of calcareous matter contained in a given weight of shells, 

 compared with the calcareous matter furnished by her food, and that dis- 

 charged as a recrement ; and, so far as these experiments go, they support 

 the opinion of a generation of lime, and that in very considerable abun- 

 dance, the weight secreted appearing to have been five times as much as 

 that introduced into the stomach. But to determine the question incon- 

 trovertibly requires so nice a precision in the mode of conducting such ex- 

 periments, as, from a variety of circumstances, it seems almost impossible, 

 to attain. 



* See also Mr. Baker-s account of the porcupine-man, Phil. Trans, (ot 1765 



