554 



REPTILE. 



is. It is true that each species of animal has fewer 

 of those laws to battle with than man has, and that it is 

 suited to the circumstances of its locality much better 

 than so universal a creature as man can be suited ; 

 but, notwithstanding this, the animal has a disad- 

 vantage under changes which man does not, and 

 cannot feel. 



In consequence of this, ready obedience to the 

 physical change is always of great advantage to the 

 animal ; and this is very clearly shown in the reptiles. 

 Their gelatinous tissues much more readily expand 

 under the action of heat than the more elastic tissues 

 of animals of more energetic systems. The tissue of 

 the lungs has already been mentioned as having but 

 little elasticity, and the same may be said of all those 

 other tissues, for the general character of the animal 

 runs through the whole ; and there is not a fibre or 

 vessel in the whole of the working structure which is 

 not sheathed with this tissue. The elasticity resists 

 in proportion to its energy, and herein lies the whole 

 difference of constitutional adaptation between the 

 reptile and the animal of more active system. The 

 elasticity resists both expansion and contraction, and 

 also the irritability of the muscular fibre as such, 

 while the more superior tissue of the reptile at once 

 gives way to any of them. sit-in 



This variableness of the elasticity of the tissue in 

 different animals is one of the most important points 

 in the whole range of animal physiology ; and yet, 

 strange to say, it is one which the professional 

 writers upon physiology have almost entirely over- 

 looked. 



It will be observed, too, that this elasticity, though 

 it must bo regarded as a product of the peculiar 

 life of the animal, because each animal has it diffe- 

 rent, according to the nature of its race, yet still it 

 is in itself a property of matter, and not a function of 

 life. If the expression be allowed, and it seems a 

 very allowable one, this same elasticity of the mem- 

 branous tissue is the anvil upon which the energy of 

 the active principle in the animal hammers out the 

 characters of its various actions ; and it would be 

 just as vain to expect that vigorous action could be 

 produced with a readily-yielding tissue, as that a 

 workman could hammer steel into shape upon an 

 anvil of lead. It is the struggle between the prin- 

 ciple of action in the animal, and the resistance of 

 the tissue, which is the real cause both of the greater 

 heat of the animal and the greater rapidity of its cir- 

 culation. The flaccid and yielding membrane will 

 not "show front" to the circulating fluid any more 

 than it will to anything else, and therefore the fluid 

 moves coldly on. So, also, the dull and passive 

 vessel will not contract on the contained fluid and 

 urge it onward, and therefore it lags and loiters. 



Applying the general principle to the reptile : it 

 is not thrown into a fever by the ardour of the 

 warmest climate, because the coats of the vessels 

 above give way to the expansion of their contents. 

 On the other hand, the vessel yields to the contract- 

 ing influence of cold, and contracts so as to stop the 

 circulation, and bring on a dormant state, without 

 almost any resistance, or. at all events, with so little 

 that the system of the creature is little injured by it. 

 It passes into a state of complete repose with very 

 little unpleasant feeling, and no injury to the system ; 

 and therefore, as soon as the cause which sent it into 

 tliis repose has ceased to act, it returns to such acti- 

 vity as may be natural to it at once, and without 



having sustained any injury, or undergone any dimi- 

 nution of substance, how long soever the time of 

 inaction may have been. Nay, though it must be 

 admitted that the point here is not so evident to the 

 judgment of " slow-going men," who have but little 

 of the anvil whereupon to hammer their own metal 

 into a weldable condition, is not altogether so clear ; 

 it is probable that this very yielding nature of the 

 tissue may enable those' reptiles which have the 

 power of momentary effort of putting on the steam, 

 as one would say to bring themselves up to the 

 high pitches of excitement under which they always 

 perform their greater efforts. We find that the 

 greater part, if not the whole of them, bring them- 

 selves up to this by the inflation or distentioi: of 

 various parts of their bodies, which makes it appear 

 that the tissue must be worked to a great extent 

 before it is able to offer the necessary resistance. 



Upon the very same principle, the reproduction of 

 members which have been taken off may be explained. 

 We know that, even in the human subject, a reduced 

 action of the system is absolutely necessary to the 

 speedy cure of wounds or cutaneous lacerations, 

 however slight. If a wounded person, or any one 

 who has a diseased part of the skin, is in very full 

 blood or vigorous action, and especially if under the 

 influence of any unnatural (and in that case not only 

 unnecessary, but injurious) stimuli, is reduced by 

 medicine, or any other cause that lowers the tone of 

 the system, the healing of the wound or the sore is 

 sure to begin, and is perfected in no very long 

 period of time. But if, while afflicted by such a 

 w r ound or such a sore, the high tone of the system 

 shall be kept up, and especially if it shall be increased 

 by tile incautious use of anything of a stimulating 

 nature, then the merest scratch may become an ill- 

 conditioned sore, and that which, in a more quiet 

 state of the system, would have healed without much 

 difficulty, may be turned into gangrenes that will 

 ultimately occasion death. 



It really does appear, therefore, that this doctrine 

 of not working the system too hard is one of the 

 most important in the whole of th:it science which has 

 for its object the promotion of health and long life 

 in animals, whether rational or irrational ; and the 

 more energetic, and therefore the more valuable the 

 animal is, the more necessary it is to attend to these 

 particulars. In the case of every animal, and of 

 course of man among the rest, there is a point beyond 

 which heat or cold, or any other kind of physical 

 action, cannot be borne. It is true that there is no 

 absolute place for this point even in the case of the 

 same species, nor do we in very many cases know 

 why some individuals have more power of endurance 

 either way than others ; but this does not in the least 

 invalidate the general principle. 



The reason of the difficulty of healing a wound or 

 a sore, under strong excitement of the system, is, that 

 the increased and turbulent circulation, restrained by 

 the resistance of the parts which are yet sound, is 

 thrown upon the weak or lacerated part, and destroys 

 the healing action which, in a more moderate and 

 healthy state of things, would be successfully going 

 on there. 



We can, without much difficult}', apply this to the 

 case of reptiles, so as to see why they should have 

 that power of reproducing a lopped member which is 

 denied to animals of more vigorous system and more 

 rapid circulation. There is, however, a preliminary 



