Fig. 104.—Scorpæna diabolus (Indian and Pacific Oceans). (After Savtschenko.)
The frogs alone exhibited, as the result of subcutaneous injection into a limb, slight transient paralysis. No effect was found to be produced by the venom when injected intravenously into the rabbit, or subcutaneously into the rat.
The poison-apparatus of Scorpæna is situated in the spiny rays of the dorsal and anal fins. These rays are enveloped in the inter-radial membrane, which forms a sheath for them, and are scored with a double cannelure. At the bottom of these grooves are the secreting cells, which are elongate, pressed one against the other, and supported at the base by a highly vascular substratum of connective tissue. The venom flows out between the layer of cells and the ensheathing membrane, which is capable of being pushed slightly back as the result of the penetration of the spine into the tissues, and then exerts pressure upon the reservoir. The latter is formed by the distension of the sheath under the pressure of the secreted liquid.
Fig. 105.—Pterois artemata (East Coast of Africa, Indian and Tropical Pacific Oceans). (After Savtschenko.)
There are twelve pairs of dorsal and three pairs of anal glands. The pairs attached to the second anal spine are, as the direct result of the size of the latter, more developed than those of the other spines.
In the Rascasse, the opercular spines of which are greatly developed, there is a rudiment of a poison-apparatus at the bottom of the sheath formed by the skin of the gills.
The species of Pterois ([fig. 105]) are distinguished from those of Scorpæna by their dorsal fins, the rays of which are very long and curved backwards, above the membrane by which they are united. They are found in the Indian and Equatorial Pacific Oceans, and are very beautiful in colour, varying from reddish-brown to bright rose.
The poison-apparatus of these fishes is situated in the dorsal fin, and is precisely similar to that of Scorpæna.