Toad-venom, therefore, contains two principal toxic substances: bufotalin, which is of a resinoid nature, soluble in alcohol, but scarcely soluble in water, and is the cardiac poison; and bufotenin, which is readily soluble in those two solvents, and is the neurotoxic poison.[161]
Pröscher, on the other hand, has extracted from the skins of toads a hæmolytic substance, termed by him phrynolysin, which possesses all the properties of a true toxin and is not dialysable. It is obtained by pounding the skins with glass powder in physiological serum.
Phrynolysin dissolves the red corpuscles of the sheep very rapidly, and (in order of sensitiveness) those of the goat, rabbit, dog, ox, fowl, and guinea-pig. The red corpuscles of the pigeon, frog, and toad are scarcely affected. When heated at 56° C. it loses its properties. By the ordinary methods of immunisation it is possible to obtain a very active antilysin.
There is, therefore, a very close analogy between the venoms of toads and salamanders. These highly complex substances are composed of mixtures of poisons, some of which are in all respects analogous to the vegetable alkaloids, while others are closely related to the microbic toxins and snake-venoms.
In the spawning season the cutaneous glands of the male toad are gorged with venom, while those of the female are empty. Phisalix[162] has shown that at this period the venom of the female is accumulated in the eggs, which, if extracted from the abdomen at the moment of oviposition and dried in vacuo, give off in chloroform a product that has all the toxic properties of cutaneous venom (bufotalin and bufotenin). No trace of this poison is to be found in the tadpoles.
B.—Lizards.
The Order Lacertilia includes only a single venomous species, which belongs to the family Lacertidæ, and is known as the Heloderm (Heloderma horridum, [fig. 124]). It is a kind of large lizard, with the head and body covered with small yellow tubercles on a chestnut-brown ground. It sometimes exceeds a metre in length, and its habitat is confined to the warm belt extending from the western slope of the Cordilleras of the Andes to the Pacific. It is met with especially in the vicinity of Tehuantepec, where it inspires the natives with very great dread. It is a slow-moving animal, and lives in dry places on the edges of woods. Its body exhales a strong, nauseous odour; when it is irritated, there escapes from its jaws a whitish, sticky slime, secreted by its highly developed salivary glands. Its food consists of small animals. Its bite is popularly supposed to be extremely noxious, but, as a rule, the wound, though painful at first, heals rapidly. Sumichrast caused a fowl to be bitten in the wing by a young individual, which had not taken any food for a long time. After a few minutes the parts adjacent to the wound assumed a violet hue; the bird’s feathers were ruffled; a convulsive trembling seized its entire body, and it soon sank to the ground. At the end of about half an hour it lay stretched out as though dead, and from its half-open beak there flowed a sanguinolent saliva. There was no movement to give any sign of life, except that from time to time a slight shiver passed through the hinder part of its body. After two hours, life seemed gradually to return, and the bird picked itself up and crouched on the ground, without, however, standing upright, and still keeping its eyes closed. It remained thus for nearly twelve hours, at the end of which time it once more collapsed, and expired.
Fig. 124.—Heloderma horridum.
A large cat which Sumichrast caused to be bitten in the hind leg did not die, but immediately after being bitten the leg swelled considerably, and for several hours the cat continued to mew in a way that showed that it was suffering acute pain. It was unable to stand, and remained stretched out on the same spot for a whole day, unable to get up, and completely stupefied.