The study of arachnolysin by Ehrlich’s methods has been undertaken afresh by Hans Sachs,[114] who has shown that rat’s and rabbit’s blood are most rapidly dissolved. Twenty-eight milligrammes of extract of Epeira are capable of completely dissolving 0·05 c.c. of blood.
By immunising guinea-pigs and rabbits, Sachs succeeded in obtaining a strongly antitoxic serum, which entirely prevents the hæmolysis of the sensitive red corpuscles.
(b) Scorpionidea (Scorpions).
The poison-apparatus of the scorpion is constituted by the last abdominal segment (telson), which is swollen and globular, and terminated by a hard, curved spine, with a very sharp point, near which can be distinguished, under the lens, two small oval orifices by which the poison is enabled to escape ([fig. 97]).
The poison-glands are two in number, symmetrically placed in cavities, each of which is completely filled by the gland. They are separated from each other by a muscular septum formed of striated fibres inserted in the chitinous skeleton; by the contraction of this septum the animal is enabled to eject its venom.
Fig. 97.—Scorpio occitanus. (After Joyeux-Laffuie.)
1, Scorpion seizing a spider, and piercing it with its sting (natural size); 2, extremity of the abdomen (telson) enlarged, showing the poison-apparatus; 3, poison-apparatus detached from the abdomen, showing an isolated poison-gland.
The scorpion never stings backwards, but always in front of itself. It delivers stabs with its sting in two distinct ways. For the purpose of defending itself from attack it elevates its abdomen into a bow, and then regains its former position by suddenly unbending it. To strike an animal, such as a spider, which serves it for food, the scorpion seizes it with its pincers and holds it as in a vice. Then it raises its abdomen, brings the end of it close to its captive, and, with a lever-like movement, drives the sting into its body. The victim immediately becomes paralysed and motionless.[115]
The poison-glands of a Scorpio occitanus from the South of France contain about 1 to 10 centigrammes of a toxic liquid, capable of furnishing 10 to 15 per cent. of dry extract. This liquid is decidedly acid; it reddens litmus paper and is miscible with water.