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point to which it is necessary to attend, as it helps to 

 throw light upon the more obscure one. If the body 

 is wounded by an instrument, or injured by any virus 

 which is not the production of a vertebrated animal, 

 and we may say not of the mammalia, to which, as a 

 class, the human body belongs, then the wound 

 closes ; and though it leaves a scar, more or less con- 

 spicuous according to the nature of the wound and 

 the mode of treatment in the curative process, yet 

 there is no absolute diminution of substance ; but, on 

 the contrary, the scam of the scar often stands higher 

 than the rest, as if there had been an accession of 

 new substance produced by the injury. But, on the 

 other hand, if a virus, originating in an animal of the 

 same genus, or even the same class, inoculates the 

 body, so as to occasion an inflamed and suppurative 

 sore, there is always a certain destruction of sub- 

 stance, the loss of which is never again supplied. 

 The simplest case to which we can refer is that of 

 a scrofulous ulcer, such as very often breaks out on 

 the lower jaw of persons who inherit that very un- 

 pleasant malady, but who, in consequence of the 

 very fact of inheriting it, appear to have the system 

 more excitable, and in a state of more constant ex- 

 citement than those in whom the body is sound and 

 free from all hereditary taint. This local outbreak 

 of scrofulous affection maybe simple, or it may be 

 severe ; but, whether it be the one or the other, if it 

 cotnes to a head and breaks, there is a pit or indica- 

 tion of the destruction of substance left, which is 

 never obliterated or rilled up, but which remains 

 with the individual for life. The only other instance 

 which we shall mention is one of foreign inoculation 

 from an animal of the same clas?, though from one of 

 a very different genus and order, namely, vaccination, 

 originally produced by the matter of a particular dis- 

 ease on the udder and teats of the cow, though now 

 transferred from <me. human being to another. I 

 this takes effect, the scar which is left in the arm, the 

 usual place to which the virus is applied, the bottom 

 of the scar is always honey-combed, as if portions of 

 4he substance had been eaten away by the virus ; and 

 if this appearance does not remain after the place has 

 been completely healed, there, to a certainty, the 

 vaccination has not taken effect. 



Now, it follows, as proof of one and -the same 

 general law, that if the body of an animal, when ino- 

 culated with a virus which occasions an unusual 

 action of the system, prevents that restoration of a 

 small quantity of local matter which would have 

 been restored to the full if the action of the body 

 had been in its usual state ; much more must a 

 system of circulation, which is naturally very slow, 

 admit of the reproduction of a member which could 

 not be reproduced with a system of greater activity. 

 Therefore we are to attribute this curious reproduc- 

 tive power in reptiles to their slow circulation as the 

 immediate cause ; though, carrying the matter a 

 little farther, this again resolves itself into the readily- 

 yielding nature of the tissue, and the gelatinous 

 nature of the whole soft parts of the body. 



These reproductions of parts have been seen in 

 natural cases, and they have been brought about, or 

 rather, scope has been given for the bringing of them 

 about, by some of the most scientific and careful 

 enquirers into the animal economy, such as Spallan- 

 r.ani, Bonnet, and Blumenbach. The experiments 

 were; made on the nimble lizard and the water-newt, 

 aud they were performed both 011 the limbs and the 



tail. Very soon after the separation of the part 

 there is an effusion of blood, though a very slight 

 one, as might be expected from the comparatively 

 small quantity of blood, and the closeness of the 

 circulation in these animals. The wound soon heals 

 without any external application, or even the pro- 

 tecting of it from the action of the air, which does 

 not appear to retard the healing process in these 

 animals of slow circulation. Soon after the hcal'intr, 

 the new member begins to sprout, and grows to the 

 proper form and size in a longer or a shorter time, 

 according to the nature of the animal, though, for a 

 considerable time, the new member looks much 

 more delicate than those which the animal possessed 

 from the beginning. This power of reproduction is 

 not confined to what is called the extremities, as, for 

 instance, the tail and the limbs, for it extends also to 

 the most delicate and nicely-formed of the organs of 

 sense. Blumenbach dissected out the eye of a water- 

 newt, which was, in due time, replaced by a new eye 

 as perfect in all its parts as that which had been 

 removed. 



The external coverings of reptiles are also worthy 

 of attention, as they are peculiar, and differ not from 

 those of any other of the vertebrated animals. This, 

 as in other vertebrated animals, consists of three parts : 

 an epidermis, or cuticle, or scurf-skin ; a derwis, or 

 cutis, or true skin : and a rete mucomm, or mucous 

 tissue. 



The two more internal of these do not differ very 

 much from the same integuments in the other ver- 

 tebrated animals, excepting perhaps in some of the 

 Batrachia, as for instance the frog and the toad, in 

 which the cutis is attached to the parts underneath 

 at only a few points, and loose like a sack at all other 

 places. This is not, however, peculiar to this batra- 

 chian reptile ; for we find instances of it in other 

 classes of animals, as for instance in the gannet 

 among birds (see the article GANNET in this work). 

 The object of this general detaching of the skin 

 from the parts under it, except at a few points, which 

 serve as ties or anchorings to keep it from shifting 

 from its proper place, appears to be that the skiu 

 may admit of inflation by the introduction of air, 

 without disturbing the economy or action of the other 

 and more essential parts of the animal. 



The epidermis, or cuticle, is much more varied in 

 its appearance and appendages ; and these are among 

 the means used for distinguishing them. The horny 

 prpductions of this part, to which the names of scales 

 or shells are given, are productions from the exterior 

 of the epidermis, just in the same manner as the hair 

 and fur of mammalia, and the feathers of birds. 

 None of them, however, are true shells, or even 

 crusts, such as occur in the shelled mollusca and the 

 Crustacea ; for they consist of consolidated animal 

 matter, without any salts of lime ; and they are al- 

 ways external of the epidermis, and not within it, as 

 are the shells of the mollusca. Of these the most 

 remarkable are the horny coverings of the Chclonia, 

 which are known as " tortoise-shell," " turtle-shell," 

 and other names, according to their quality, which 

 depends upon the species by which they are pro- 

 duced. Though we say that these productions are 

 " horny," as distinguished from bones and shells, both 

 of which have the carbonate or the phosphate of 

 lime, or both, in their composition, we must not con- 

 found them with the form which is found in the 

 horns, hoofs, and claws of the mammalia, and in the 



