Ml 



AMPHIBIA. 



AMPHIBIA. 



164 



their small month is furnished with homy hooka or teeth for the separa- 

 tion at vegetable nuttier, and tlicy have a nuall tube on the low.-r lip 

 by which they attach themselves to aquatic plant*, *c. The external 

 branohuB next disappear, and become covered with a membrane, 

 being placed in a sort of sac under the throat ; and the animal then, 

 a* w have observed when treating of its respiration, breathe* after 

 the manner of fishes. The head, which in furnished with eyes and 

 nostrils, is confounded with the Urge globulnr trunk distended with 

 the great extent of the digestive canal, and it has a large tail for 

 swimming. In this state it ia called in Kiiglixli a Tadpolf, and in 

 French Ttlard, from the great apparent volume of the head. Soon 

 the posterior limbs are gradually put forth ne*r the origin of the 

 tail, and are developed timt ; tho anterior feet then begin to show 

 themselves ; the tail gradually becomes less and less, shortens, nliriiiks, 

 and seems at last to be absorbed ; the mouth widens, and loses its 

 horny processes or jaws ; the eyes are guarded by eyc-liil* ; the belly 

 lengthens and dimiuinhes in comparative si/.u ; the intextincs become 

 short ; the true lungs are developed, and the internal brand > 

 obliterated; the circulation undergoes an entire change; ami tin- 

 animal, hitherto entirely aquatic and herbivorous, becomes carnivorous, 

 and for the most part terrestrial. 



Mr. Thomas Wharton Jones ('Zool. Proc.,' March, 1837) observes, 

 that whan the right gill of the Tadpole disappears, it is not, as is 

 usually supposed, by the closure of the fissure through which it 

 protrudes, but by the extension of the opercular fold on the right 

 aide towards that of the left, forming but a single fissure, common 

 to the two branchial cavities, through which the left gill still pro- 

 trudes. He also remarks, that conditions analogous to those which 

 occur during several stages of this process exist in the branchial 

 fissures of the Anguilliform genera, Sphayeliranchtu, Manoptenu, and 



Particular Excreiiont. The alleged venom of the Common Toad, 

 BO long a subject of popular belief, had been rejected by many modern 

 naturalists, among whom Cuvier may be particularly mentioned. Dr. 

 Davy, however, found the venomous matter to be contained in 

 follicles, chiefly in the true skin and about the head and shoulders, 

 but also distributed generally over the body and on the extremities. 

 Pressure causes this fluid to exude or even spirt out to a considerable 

 distance, and a sufficient quantity may be thus collected for examina- 

 tion. Dr. Davy found it extremely acrid when applied to the tongue, 

 resembling the extract of aconite in this respect ; and it even acts 

 upon the hands. With a small residuum it is soluble in water and in 

 alcohol ; acetate of lead and corrosive sublimate do not affect the 

 solutions. It remains acrid on solution in ammonia; and when 

 dissolved in nitric acid, it imparts a purple colour to it. Combined 

 with potash or soda, it becomes less acrid, apparently in consequence 

 of partial decomposition. It is highly inflammable OB left by evapora- 

 tion of its aqueous or alcoholic solutions ; and the residuum which 

 appears to give it consistence seems to be albumen. More acrid than 

 the poison of the most venomous serpents, it produces no ill effect 

 when introduced into the circulation. A chicken inoculated with it 

 was not affected. Dr. Davy conjectures that this ' sweltered venom' ia 

 a defence to the Toad from carnivorous animals ; and we have seen a 

 dog, when urged to attack one without hesitation, drop the animal 

 from its mouth in a manner that left no doubt that he had felt the 

 effects of this excretion, which Dr. Davy thinks may be auxiliary in 

 decarbonising the blood. 



The Toads are also said to possess, besides, two glandular masses 

 (parotids), which, when pressed, exude through small holes a yellowish 

 thick humour of a musky odour. The other odours also which ninny 

 species of Toads produce, it does not seem yet ascertained from what 

 source, are very remarkable. Roesel, author of the beautiful work MM 

 Frogs, compares some of these to the smell of garlic or of volatilised 

 sulphur of arsenic, or even ignited gunpowder; others again, he says, 

 produce an effect on the nose like the vapour of horse-radish, mustard, 

 or the leaves of monk's-hood rubbed between the fingers. In one 

 instance only he states it to be probable that this emanation 

 comes from the cloaca; and such seems to be the opinion of M. 

 Dumeril, who states that he has been assured that, in certain 

 instances, the water in which some of these animals had been placed 

 and there purposely irritated or excited, had become so acrid that the 

 Ud|>oles of frogs and salamanders introduced therein hardly survived 

 the immersion. 



Geographical Dit(ril>ulion and ffaliit. Warm and temperate but 

 moist climates arc the localities most favourable to the Anourou* 

 Amphibia. Extreme cold is fatal to them, and so is extreme dry 

 heat. They are unable to sustain violent and sudden changes of 

 temperature. In moderately warm climates, and those where there ix 

 a considerable degree of cold during a part of the year, they bury 

 themselves, in winter, either under the earth or in the mud at the 

 bottom of the water, and there pass the season of hybonmtion 

 without taking food or air, till the spring calls them forth ; when the 

 same frog which had passed so many months without rex; 

 would expire in a few minutes if prevented from shutting its month 

 and so supplying itself with air by deglutition. The general habits of 

 the tribe may be collected from tl .MM nf thix article, 



and from the dexcriptiotiH of those forms in it which may be noticed 

 in the course of thin work. 



The following cuts will convey to the reader an idea of some of 

 the leading forms among the A nottroiw A mj>At'6i'a in their adult state : 



Marnh Frog (Ilann pahitlrii). Tiro-thirds natural nizr. Europe. 



Crralophrys granosa. Two-thirds natural ize. America. 



Common Toad (Bi</b rulgarii). Half natural niste. KIIVIIK-. 

 With un under view of the foot. 



Ifl/ltt !,<r::l:,r. 1 I til f Wit 111 111 HW. SolltllAllH 



