The Decapods (cuttle-fishes [_Sepia_], &c.), have only posterior salivary glands, of smaller dimensions in proportion to the size of the body. On being crushed and macerated in water, the anterior glands yield a limpid and slightly acid juice; the posterior glands produce a viscid, ropy fluid, filterable with difficulty and neutral. The latter has an immediate paralysing effect upon Crustacea. It contains a substance of a diastasic nature, precipitable by alcohol, and destructible by heating for an hour at 58° C. Owing to the poisonous properties of this juice, Octopods succeed in overpowering large prey, such as lobsters and crabs. Once they are seized by the tentacles of the octopus, or cuttle-fish, a bite inoculates these animals with venom that immediately destroys their power of movement, and the Cephalopod is able to continue its meal in perfect security, without having to fear the pincers of its prey. An experimental study of this venom has been made by A. Briot,[137] who found that crabs are very sensitive to it, while rats, frogs, rabbits, and fish do not appear to experience any inconvenience. CHAPTER XVII. _VENOMS IN THE ANIMAL SERIES_ (_continued_). 2.--_VENOMOUS FISHES._ The means of defence in fishes are extremely varied. Some species (torpedoes or electric rays, electric eels) destroy their enemies by electric discharges; others are provided with true poison-glands and inoculatory organs, usually represented by opercular spines or by the fin-rays. The species of the genus _Muræna_, however, possess a poison-apparatus connected with the buccal teeth, as in the case of snakes. It has been clearly established by Bottard[138] that at least three very distinct types of venomous fishes exist, according as the venom-apparatus is:-- (1) Entirely closed (_Synanceia_ type); (2) half closed (_Thalassophryne_ type); (3) in more or less direct communication with the exterior (_Trachinus_ and _Scorpæna_ type). The greater part of the following statements has been borrowed from the excellent work of the author referred to, from the writings of A. Corre,[139] the fellowship thesis of Henry Coutière,[140] and the magnificent atlas published at St. Petersburg in 1886 by P. Savtschenko, of the Russian Imperial Navy. Except in the case of the species of _Muræna_, the venom of fishes is generally found in one or more special glands, situate at the base of the dorsal or caudal fins, or beneath the opercular spines. When the animal defends itself it inflicts wounds with these rays, and ejects from its poison-glands a toxic or irritant liquid, which enters the sores.