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.

The flesh of these fishes is not usually poisonous, whereas a fairly large number of other species, _which do not inflict wounds_, cause intoxicating effects when eaten. These latter do not come within the scope of this work; but the reader who may desire to obtain information with regard to them will find them well described in J. Pellegrin’s memoir,[141] in that by Dupont, and especially in the papers of A. Corre.

_Venomous fishes_ almost all belong to sedentary species, as in the case of the genera _Trachinus_, _Cottus_, _Scorpæna_, and _Synanceia_. This fact suggested to Dissard and Noë[142] a very hazardous theory in order to explain the existence of a poison-apparatus in these animals. The venomous fishes being sedentary, say these authors, have no need of a poison-apparatus; their prey offers itself to them without effort on their part, and, on the other hand, they escape destruction by their enemies. If, therefore, they possess a poison-apparatus it is because the conditions under which they live entail the lowest value for the co-efficient of respiration, diminish the quantity of the ambient radiations and the oxygenation of the medium, and lead to diminished hæmatosis. For these reasons the activity of anaerobic life becomes greater, and the formation of venoms takes place.

This theory, derived from the conceptions of A. Gautier with regard to the formation of toxic leucomaines, appears scarcely tenable, for it is evident that the weever, for example, erects its first dorsal spine as soon as it is seized, and that _Scorpæna_ and _Synanceia_ likewise protrude their venomous spines when conscious of danger. The poison-apparatus of these fishes is therefore of an eminently defensive character.

According to Bottard, the spawning season increases the activity of the poison-glands and at the same time the toxicity of the secreted product. Several species, such as those of the genus _Cottus_ and the perch, possess no apparent secreting cells except at this period. Certain _toxicophorous_ or poisonous fishes, such as the species of _Tetrodon_, are particularly noxious at the time when their genital glands are at their maximum activity.

A.--TELEOSTEI.--ACANTHOPTERYGII.

1.--=Triglidæ.=

The fishes of this family are all repulsively ugly. They have an elongate and but slightly compressed body, covered with ctenoid scales, and a large head in which the suborbital bones, which are broad, unite with the præopercular so as to form an osseous plate in the malar region. The pectoral fins are large, and provided with a few detached rays, which perform the function of tactile organs; the ventral fins are situate on the breast. These fishes are extremely voracious.

The most interesting type is the _Synanceia_ termed by the Creoles of Réunion _Crapaud de mer_, and by those of Mauritius _Laffe_. In Java it is called _Ikan-Satan_ (Devil-fish), and in Tahiti _Nohu_. It is distributed throughout almost all the warmer regions of the Indian and Pacific Oceans, and is found in Cochin-China and New Caledonia.

It is never taken in the open sea, but only among the fringing reefs, where it lives constantly concealed in holes or buried in the sand. It does not come out except to make a sudden dart at prey passing within its reach. When irritated it does not eject venom; for the latter to be expelled one has either to press hard upon the poison-sacs, after pushing back with the fingers the membranes covering the dorsal defensive armature, or the naked foot must be placed on the back of the fish. The wound is very painful, and is accompanied by a series of alarming symptoms, which sometimes terminate fatally: fishermen are consequently much afraid of it.

There are a large number of species of this fish, peculiar to different regions. _Synanceia brachio_ (fig. 101), the largest specimens of which attain the length of 45 cm., is the most common form in the Tropical Pacific.

The spiny rays of the dorsal fin of _Synanceia_ are sharp-pointed, stout in the middle, and provided on each side with a small canal hollowed out in the thickness of the spine. Towards the middle of the latter there is attached a little double sac, or kind of closed pouch, which, on being compressed, allows the venom to escape in a thin jet which flows into the grooves of the spine. The expulsion of the venom is therefore not a voluntary act on the part of the fish; in order that it shall take place, pressure must be applied to the sacs in which it is contained.

This venom, when extracted from the glands, is limpid, bluish, and slightly acid. When introduced into the tissues, it produces very acute local pain, which extends throughout the affected limb. The pain is excruciating, and sufferers have been observed to become actually delirious, striking and biting those around them, throwing themselves from side to side, and beseeching that the limb should be cut off; some of them have amputated the injured part themselves.

This condition is accompanied by considerable anxiety, and by attacks of leipothymia and sometimes of syncope. In some cases syncope has been followed by death; in others serious phlegmons, complicated by septicæmia, supervene. The inoculated spot becomes bluish, and then sphacelates over a larger or smaller area. These gangrenous wounds heal very slowly, more especially since they are usually produced on the sole of the foot (Bottard).

A single drop of the venom is sufficient to kill frogs in about three hours.

The genus _Cottus_, which also belongs to the family TRIGLIDÆ, includes some forty venomous species found in the seas of the northern hemisphere, in Europe, Asia, and America.

In France the species of _Cottus_ are generally called _chabots_ (bullheads or miller’s thumbs), _chaboisseaux_ (sea-scorpions), or _caramassons_. They are abundant on the coast of Normandy, and some of them (river bullheads) live in fresh water; they do not exceed 25 cm. in length. They have a liking for holes in rocks, and fishermen are afraid of being stung by them (fig. 102).

Their poison-apparatus resembles that of the Weevers, but is less developed. It is situated in the culs-de-sac formed by the opercular spines. The culs-de-sac are lined with cells which produce a toxic secretion only during the spawning season, from November to the end of January. This fact explains how it is that the species of _Cottus_ are declared by certain fishermen to be very venomous, while others say that they are absolutely harmless.

The genera _Scorpæna_, _Pterois_ and _Pelor_ also belong to the same group.

In _Scorpæna_ the body is clothed with scales, and the head is large, slightly compressed, armed with spines, and has a bare pit behind; the single dorsal fin is provided with eleven spiny rays, and there are seven branchiostegal rays. _Scorpæna grandicornis_ (fig. 103), found in the Caribbean Sea, is from 30 to 50 cm. in length, and has the back red and the eyes and belly yellow; _Scorpæna diabolus_ (fig. 104), which occurs in the Indian Ocean and Tropical Pacific, is red and brown, obliquely striped with white and brown; a third species, _Scorpæna porcus_ (_Scorpène truie_), of smaller size, is met with in the Mediterranean. The venom of the latter has been studied by A. Briot,[143] who sectioned the dorsal and opercular spines, and macerated them either in physiological saline solution, or in glycerine; he then tested the toxicity of these macerations on certain animals--frogs, rabbits, and rats.

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.

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_.

The species of _Pelor_ (fig. 106) present greater resemblance to those of _Synanceia_, owing to their heads being crushed in in front. Their eyes stand up above the head and are very close together, which helps to give them an extremely ugly appearance. The skin is soft and spongy, and bristles with jagged fleshy shreds.

Their poison-apparatus is placed in the dorsal fins, as in the case of _Scorpæna_ and _Pterois_.

2.--Trachinidæ.

Genus _Trachinus_ (Weevers).--Four species of Weevers are found in European seas: the Greater Weever (_Trachinus draco_), the Lesser Weever (_T. vipera_), the Striped-headed Weever (_T. radiatus_), and the Mediterranean Spider Weever (_T. araneus_); other species are met with on the coast of Chile.

Weevers possess two sets of poison-apparatus, one of which is situated on the operculum, the other at the base of the spines of the dorsal fin (fig. 107).

The spine surmounting the operculum exhibits a double cannelure connected with a conical cavity excavated in the thickness of the base of the opercular bone. This spine is covered with a sheath, beneath which lie the secreting cells. The gland is an offshoot from the skin, and appears as a simple follicle invaginated in the opercular bone (fig. 108).

The dorsal apparatus is composed of from five to seven spines, to which the inter-radial membrane forms an adherent sheath which extends almost to the end of the rays. Each spine exhibits a deep double cannelure. The venom flows between the layer of cells clothing the cannelures and the skin, which is distended to allow it to pass.

Towards the base of the spine, the edges of the cannelure are united, and form a hollow, bony cone, the walls of which are lined with the cells that secrete the toxic fluid.

Greater Weevers are usually from 12 to 30 cm. in length, and of a reddish or yellowish-grey colour, with blue or violet spots. They are caught in trawls and are fairly common on sandy bottoms. In the month of June they approach the shore for the purpose of spawning.

The venom of the Weever has formed the subject of interesting studies by Günther, Gressin,[144] Bottard, Phisalix,[145] and more recently by Kobert[146] and A. Briot.[147]

In order to procure sufficient quantities of it for experimental purposes, Briot cuts off the venomous spines and the surrounding tissue with a pair of scissors; he then pounds the whole in a mortar, and mixes the pulp with pure glycerine. After filtration through paper, a toxic solution is obtained, which does not deteriorate by keeping, and is neutral to litmus.

A few drops of this liquid are sufficient to kill guinea-pigs, which, immediately after receiving an injection in the thigh, exhibit paralysis of the leg with tetanic convulsions; twenty-four hours later an eschar is formed, and death supervenes on the second or third day.

Two or three drops, introduced into the marginal vein of the ear of a rabbit, cause death from asphyxia in from four to ten minutes. The heart continues to beat for a fairly long time after respiration has entirely ceased; the blood is not coagulated.

The toxicity of this venom is completely destroyed by heating it to 100° C., by chloride of lime, and by chloride of gold. Antivenomous serum prepared from horses vaccinated against cobra-venom has absolutely no effect upon it _in vitro_. There is therefore no affinity between this venom and that of snakes.

Weever-venom dissolves the red corpuscles of the horse in the presence of normal heated horse-serum, but does not dissolve them in the presence of fresh serum. The non-heated serum, therefore, as I have shown with reference to the action of cobra-venom on the blood, contains a natural antihæmolysin.

Briot succeeded in vaccinating rabbits by accustoming them to the venom, and in obtaining from them a serum capable of neutralising the latter _in vitro_, and of immunising fresh rabbits against doses several times lethal, even when injected intravenously.

According to Gressin, the following phenomena are produced in man as the result of Weever-stings:--

“At first there is felt an excruciating, shooting, paralysing pain, which, in the case of nervous persons, may cause attacks of leipothymia ending in syncope. A kind of painful formication next pervades the injured limb, which becomes swollen and inflamed, and may even, if treatment be neglected, form the starting point of a gangrenous phlegmon.

“This condition is frequently accompanied by certain general phenomena--such as fever, delirium, and bilious vomiting, the duration of which is variable, since they may only last for two or three hours, or may continue for several days. Fishermen rightly consider this variability to depend upon the amount of venom that has penetrated into the wound, and especially upon the season at which the accident takes place. The most serious results are recorded during the spawning season, and fishermen regard the Lesser Weever as being the more poisonous.”

3.--Gobiidæ.

In the fishes belonging to this family the body is elongated and depressed, while the spines in the anterior dorsal fin and in the ventral fins are slender, flexible, and seldom very solid. The ventral fins are inserted on the breast or on the throat, and are either separated or united together in the shape of a funnel. The skin is naked or covered with large scales, and the mouth is furnished with teeth. The males are distinguished by the presence of a long genital papilla. These fishes are carnivorous.

Several species of venomous =Gobiidæ= are met with on the shores France and in the tropical zone. The most important of these belong to the genus _Callionymus_ (_C. belennus_, _C. lacertus_, _C. vulsus_, and _C. lyra_--fig. 109).

The Dragonet or Skulpin (_Callionymus lyra_), which is common on the coast of Calvados, may attain the length of 30 cm. In France it is popularly known as the _Doucet_, _Dragonnet_, _Lavandière_, _Cornaud_, or _Capouri_. Its colours are very vivid, orange and deep lilac.

In this fish the præopercular bone ends in three strong, conical, and very sharp points, diverging like the prongs of a trident. The upper margin of the opercular bone bears another point, which is directed upwards.

The skin of the gills forms a common sheath for this defensive armature, and the base of the sheath is prolonged into two culs-de-sac, the surface of which is clothed, during the spawning season, with cylindrical cells, the secretion of which is poisonous.

This venom, which is small in amount, does not appear to have any marked effect upon man (Bottard).

4.--Teuthididæ.

This family of _Acanthopterygii_ includes several species of brilliantly coloured fishes with elongated and laterally compressed bodies, provided with a long dorsal fin, and having, on each side of the tail, a sharp spine placed in front of the anal fin. They are herbivorous, and are confined to the tropical seas.

The principal genera are: _Teuthis_ (India), _Acanthurus_ (Tropical Atlantic), _Prionurus_ (Japan), and _Naseus_ (Red Sea and Indian Ocean). The fishermen of Réunion are much afraid of the wounds inflicted by _Acanthurus luridus_, which they call _Marguerite Porc_ or _Grande Marguerite_. A sting from this fish causes a very acute smarting pain, which may last for several hours, but usually has no serious consequences.

The poison-apparatus of these fishes is situated in the dorsal and anal fins, as in _Scorpæna_.

5.--Batrachiidæ.

The venomous species belonging to this family are few in number. They are found in all tropical seas, but have no representatives in Europe. The best-known species are _Batrachus tau_ (shores of Central America), and _B. grunniens_, or Grunting Batrachus (fig. 110).

The Grunting Batrachus, which does not exceed 30 cm. in length, is especially common in West Indian waters. When taken from the water it makes a peculiar grunting sound, whence its name is derived. The pectoral fins are reddish, the back is brown, and the sides are yellow, marbled with black. It has three spines in the anterior dorsal fin, and a fourth spine on the top of the operculum, with a small poison-sac at the base of each.

Next to this genus come the species of _Thalassophryne_, _T. reticulata_ (fig. 111), found on the shores of Panama, and _T. maculosa_, of Bahia (Brazil), which are provided with a precisely similar poison-apparatus.

The physiological action of the venom of these two species has not yet been studied, but it is probable that it does not differ from that of the venom of the Weevers and the species of _Synanceia_.

6.--Pediculati.

The fishes belonging to this family are of large size and compact shape, with the anterior part of the body greatly expanded. The head, which is broad, bears venomous spines, and the mouth is furnished with large teeth. These fishes are voracious, and lie in wait for their prey at the bottom of the water in the mud of the shore. In order to attract it, they make use of cutaneous appendages attached to their spines, which they are able to elevate, and of filaments situated near the mouth.

The principal genus is _Lophius_, one species of which, _L. setigerus_ (fig. 112), is found in the seas of China and Japan. Another species, _L. piscatorius_ (the Sea Devil or Angler), occurs in the temperate climates of Europe, North America, Asia and Africa.

Certain other _Acanthopterygii_ are _capable of inflicting wounds_, but, although fishermen often believe them to be venomous, or such properties are frequently attributed to them in stories, it is doubtful whether they possess poison-glands. The accidents produced by them are due rather to the fact that the spines in their fins are extremely sharp, and that their flesh is toxic. Those belonging to the _Percidæ_ (the Perch family), especially the genus _Serranus_ and _S. ouatabili_ (fig. 113) in particular, are above all remarkable in this respect. The last-mentioned fish has two or three spines on its operculum.

The same may be said of certain _Squamipinnes_, another family of _Acanthopterygii_, whose stout bodies are brightly coloured, and have very sharp, spiny rays in their dorsal and anal fins. The most curious genus among the fishes belonging to this family is _Holacanthus_, in which the præoperculum is provided with an enormous spine like that of the Weever. _Holocanthus imperator_ (fig. 114) is met with fairly often in the Indian Ocean and Malay Archipelago.

B.--TELEOSTEI.--PLECTOGNATHI.

The Order _Plectognathi_ (Family _Gymnodontes_) includes the genera _Diodon_, _Tetrodon_ and _Triodon_, globular fishes, in which the jaw is transformed into a beak and furnished with a sharp dentary plate. Their œsophagus is dilated into a resonant air-pouch. When removed from the water they swallow air and dilate the pouch, and the expulsion of this air is accompanied by a loud noise.

Several species of _Tetrodon_ are armed with spines, which produce very painful wounds. Their flesh is toxic, but it has not been proved that poison-glands exist at the base of the spines.

On the shores of the Cape of Good Hope, Brazil, China, and Japan these fishes are much feared. The principal species are _Tetrodon stellatus_ (Indian and Pacific Oceans; fig. 115) and _T. rubripes_ (Japan; fig. 116).

Closely allied to _Diodon_, and feared like the foregoing on account of their spines, which are sometimes scattered all over the body, are the species of the genus _Chilomycterus_, the most important of which are _C. orbicularis_ (fig. 117), and _C. tigrinus_ (fig. 118), both of which are found in the Indian Ocean.

C.--TELEOSTEI.--PHYSOSTOMI.

This Order is characterised by the presence of a pneumatic duct to the air-bladder. It consists of a large, number of families, only two of which, the _Siluridæ_ and _Murænidæ_, include venomous species.

1.--Siluridæ.

The majority of the very large number of species belonging to this family live in fresh water, and have the free margin of the lips almost always furnished with barbules (_Silurus glanis_; fig. 119). A few of them possess a poison-apparatus, which, however, attains its greatest development in _Plotosus_, the only genus of Siluridæ found exclusively in the sea.

The species of _Plotosus_ frequent the shores of the Indian Ocean, and are met with in the Seychelles, Réunion, and Mauritius. In shape they resemble eels, and they bury themselves in the sand or mud, a habit which renders them very dangerous to fishermen.

_Plotosus lineatus_, which is of a greenish-brown colour, striped with from four to six longitudinal whitish bands, is the most common. By the Creoles of Mauritius and Réunion it is called _Machoiran_, by the Malays _Sambilang_, and by the Abyssinians _Koomat_.

Its poison-apparatus is situated at the base of the dorsal and pectoral spines. These spines are strong, sharp, slightly incurved, and furnished with hooked denticulations, which cause them to remain in the wound, in which they break off. Near their extremity there opens a small canal, which communicates with the culs-de-sac situated at the base of the spiny rays, which produce a venomous secretion. The dorsal spine has only a single cul-de-sac, while the pectoral spines have two.

The contraction of the local muscles, by compressing these culs-de-sac, can cause the venom to make its way into the canal of the spine, but the fluid does not spurt forth in a jet as in the case of _Synanceia_. The poison-apparatus is therefore passively defensive in character. _Plotosus_ is capable of wounding only when the hand or foot is placed on its dorsal or pectoral spines.

Fishermen who are stung immediately feel an excruciating pain, which is soon accompanied by fever, and lasts for several days. Accidents caused by this fish are of fairly common occurrence in Réunion.

2.--Murænidæ.

Of the fishes belonging to this family, the species of the genus _Muræna_ alone concern us. They have an elongated body, without pectoral fins, and a naked skin, covered with a thick layer of viscid slime, as in the case of the eels. Their dentition is powerful, formed of long, recurved fangs, arranged in one or more rows. These fishes may attain a large size, exceeding 2 metres in length. More than one hundred species are known, all of which live in tropical or subtropical seas. _Muræna helena_ is common in the Mediterranean in the vicinity of Nice and Toulon; _M. moringa_ (fig. 120) is found in the Tropical Atlantic.

The species of _Muræna_ live in deep water, and feed upon fishes or crustaceans. In hot countries they frequently venture into fresh water. Their skins are adorned with brightly coloured markings, which vary very greatly according to the species.

The poison-apparatus in _Muræna_ consists of a pouch situated above the membrane of the palate, which may contain ½ c.c. of venom, and three or four conical, curved teeth, with the convex surface in front, as in the fangs of snakes. The teeth are not pierced by a central canal, and the venom flows between them and the mucous membrane of the palate, which forms a sheath. The latter is withdrawn to the base of the teeth, while they are penetrating the tissues. The teeth are mobile; they are articulated with the palatine bone, in which they are inserted in small depressions, and a resistant fibrous tissue serves as the means of union. They can be deflexed backwards against the mucous membrane of the palate; in this position the first, second and fourth tooth (when the latter exists) disappear completely between the folds of the membrane. The third tooth normally remains erect, and it is this by which wounds must in most cases be inflicted. None of these teeth can be protruded beyond the vertical.

In addition to the palatine teeth there are, among the groups of maxillary teeth, several mobile teeth, which are connected with the poison-reservoir.

Besides its toxic action the venom of _Muræna_ has manifest digestive properties, and, in the case of a fish which has been dead for some little time the gland is no longer to be found, since its walls have undergone a rapid autodigestion.

The venoms of all the fishes of which I have just given a brief description, as regards their physiological action, present a fairly close resemblance to the venom of the Weever, and show scarcely any variation except in the intensity of their effects. They have been but little studied hitherto, and it is desirable that they should be better understood.