The venom secreted by salamanders evidently serves to protect these creatures against their enemies. So long ago as 1866, Zaleski[149] isolated from it a substance soluble in alcohol, insoluble in ether, and with a very strong alkaline reaction, to which he gave the name salamandarin. This substance, which is better known to-day as salamandrine, has been studied afresh by A. Dutartre,[150] Phisalix and Langlois,[151] and subsequently by Edwin and S. Faust.[152]
Fig. 123.—Cryptobranchus japonicus (Great Japanese Salamander).
The action of this poison on the frog is characterised by a period of violent convulsions, with general tetanic crises, followed by a period of paralysis, with arrest of respiration and complete muscular relaxation. According to the quantity of poison absorbed, this paralytic period may be followed by death, with arrest of the heart in diastole, or else by return to life, with more or less acute recurrence of convulsions.
S. Faust prepares salamandrine by pounding up whole salamanders in a small quantity of physiological saline solution. The thick pulp obtained in this way is filtered. One cubic centimetre of the filtrate, taken as a unit, contains about 5 decimilligrammes of active substance, which can be purified by treating the filtrate with alcohol, which dissolves the salamandrine and precipitates all the proteic substances that give biuret reaction. The salamandrine thus freed from proteins is saturated with sulphuric or phosphoric acid, when there is formed a crystallisable salt, which is washed and dried. This salt is soluble in alcohol and in water. Its chemical composition is as follows:—
C52H80Az4O2 + H2SO4.
The toxicity of this substance is such that from 7 to 9 decimilligrammes per kilogramme represent the lethal dose for dogs, when injected subcutaneously. The lethal dose for the rabbit is still smaller. It produces convulsive phenomena, followed by arrest of respiration. The administration of chloral to the subjects of the experiment, either preventively or immediately after the poison, prevents the latter from taking effect. Besides salamandrine, S. Faust has isolated a second alkaloid, salamandridine, which, as a sulphate, corresponds to the formula (C20H31AzO)2 + H2SO4, crystallises in rhombic prisms, and is soluble with difficulty in water. The only difference between the two alkaloids is formed by a methylpyridic group, and both are derivatives of quinoline. They must therefore be considered as identical with the exclusively vegetable alkaloids.
S. Faust concludes from his physiological investigations that salamandrine takes effect upon the central nervous system, especially upon the respiratory centres. It is a convulsion-producing poison, comparable to picrotoxin, but its effects differ from those of the latter substance in that the convulsions are accompanied by tetanic spasms.
The venom of the Japanese Salamander (Cryptobranchus japonicus) has formed the subject of studies by Phisalix.[153] This investigator has shown that this venom, which is highly soluble in water and in glycerine, is very unstable; alcohol and heating for twenty minutes at 60° C. are sufficient to destroy it. When inoculated into frogs it produces œdema and hæmorrhage; if injected into warm-blooded animals it causes necrosis. In sufficiently strong doses it kills by arresting respiration. Its effects strongly resemble those produced by Viperine venoms. This venom, if attenuated by being heated at 50° C. and injected into mammals, vaccinates them and leads to the formation in their blood of antitoxic substances, which are capable of preventing intoxication by salamander-venom, and, curiously enough, also confer immunity against viper-venom and the serum of the common snake.
Toads are easy to distinguish from frogs owing to their squat and clumsy shape, and to the mass of glands with which each side of the neck and a more or less extensive portion of the body is furnished in these animals. According to G. A. Boulenger, the number of known species amounts to seventy-six, which are found in the Old and New Worlds, but have no representatives in Australia. The species that are the most common, and most interesting from the point of view of their venoms, are:—