156 ICHTHYOLOGY. 



SECT. IV THE MUSCLES AND MUSCULAR MOTIONS OF coiisequence of the projection of the upper and under Introduc 



FISHES. spiny processes of the vertebrae. tion. 



Tlie great organ of movement in all fishes is the tail. **^'^'^~' 



The spinal column, composed of numerous articula- The muscles by which it is brought into play extend in 



tions united by cartilages which permit of certain move- lengthened masses on either side of the vertebral column. 



ments, curves with great facility from side to side ; but The body being supported chiefly by the swimming blad- 



the vertical motion is much more restricted, chiefly in der (which, however, is absent in several species), is pro- 



temporal system : Palatine, 22 ; temporal, 23 ; transverse bone, 24 ; internal aptervgoidean, 25 ; jugal, 26 ; tympanal, 27. Opercular 

 bones: Operculum, 28 ; styloid, 29 ; pre-operculuni, 30; sympletic, 31 ; sub-operculum, 32 ; inter-opereulum, 33; this last-named 

 bone furnishes an attachment to the branch of the hyoid bone at the point where it is itself joined to the styloid, which suspends it 

 on the temporal bone, and hence the opercular sliutters can neither open nor close without a corresponding movement of the hyoidean 

 branches. Lower ja-w : Dental, 34 ; articular, 35 ; these are the usual divisions, but there is often a third bone, the angular, 36", 

 and sometimes a fourth, on the internal face of the articular, con-esponding to the opercular of reptiles, 37. Thus the head of 

 fishes usually consists of about sixty bones — the amount being sensibly greater in such species as have the upper maxillary subject 

 to division. 



Hyoid bone and branchiostegous rn?/s. The three opercular pieces above mentioned do not of themselves effect the closure of those 

 great clefts observable on each side of a fish, between the head and shoulder, and within which are the respiratory organ sor bran- 

 chije. This closure is completed by the branchiostegous membrane, which adheres to the hyoid bone. (See Plate CCXCVII. figs. 2, 

 4, and 5.) This bone is placed as in other vertebrated classes, but is always suspended to the temporal bones. It is composed of 

 two branches, each consisting of five pieces, viz. the styloid, 29, by which it is suspended to the temporal ; two large lateral pieces, 

 37 and 38, placed one behind the other, and forming the principal portion of the branch (the posterior, 38, being that which attaches 

 to the inter-operculum) ; lastly, two small pieces, 39 and 40, placed one above the other at the anterior extremity of the branch, 

 and serving to unite it with the corresponding portion of the other side. Anterior to this junction is the lingual bone, 41, and be- 

 hind it, in the angle formed by the meeting of the two branches, and beneath the branchiiE, is a single piece, usually vertical, 42 (fig. 

 5), which represents the tail of the hyoid bone, so well known in birds and liz.irds. It is this piece which, uniting with the sym. 

 physes of the humerals, forms what is called the isthmus, which separates the two branchial openings from below. Thus in its tota- 

 lity the hyoid bone of fishes is composed of twelve bones. 



The rays, 43, which support the branchiostegous membrane, adhere by moveable articulation, or by simple ligaments, to the infe- 

 rior margin of the principal portions already mentioned (37, 38) of the hyoid bone. They vary in form and number, some species 

 having three, others thirty. The perch, which forms the subject of our illustration, has seven branchial rays ; and that number is the 

 most common among the acanthopterygian fishes. 



Bones iehich support the branchlcr. As fishes cannot respire except by making the water which they have taken into the mouth flow 

 out by the openings behind the lateral part of the head, it thus passes between the branchine, those well-known comb-like organs, 

 usually four in number on each side, composed of a great quantity of thin, narrow, forked laminte, of a membranous or cartilaginous 

 nature, and placed in files. These four pair of branchiae are supported by four pair of arches, adhering by their inferior extremities 

 to the two sides of a chain of small intermediate bones, which is itself attached to the angle formed by the anterior portions of the 

 hyoid bone, and above the tail of the latter. These arches ascend in a curve, and are attached at their other extremity beneath the 

 cranium, but by means only of cellulosity, or of ligaments. The intermediate chain of bones just alluded to forms, in a certain sense, 

 a continuation of the lingual bone. There are usually three : the first, 53 (see chiefly fig. 4), is attached at the base of the angle formed 

 by the two branches of the hyoid bone ; the second, 54, affords attachment to the first pair of arches ; and the third, 55, affords the like 

 attachment to the second pair, while the third pair adheres to its extremity ; the fourth pair of arches is connected with the angle of the 

 third pair. Each arch is composed of two parts, moveable on each other, and the interior portion of the first three pair itself consists 

 of two pieces, 57 and 58 ; in the last pair there is only a single piece, GO. The upper portion of the arches, CI, is simple, except in 

 the first pair, which is usually suspended from the cranium by a small stylus, 59. The inner face of these arches is furnished with 

 small plates or cones of osseous lamina, usually armed with teeth variously disposed according to the species. The most general uses 

 of this armature are to arrest the progress of such substances as the fish is swallowing, — to prevent their escaping with the respired 

 water, or their producing inconvenience amid the interstices of the branchia;. It may be likened in its functions to the epiglottis of 

 quadrupeds, or the dentations of the margins of the larynx of birds. Besides the interior range of conical plates, the perch possesses 

 an external row of slender pointed teeth, resembling those of a garden rake, upon its first pair of arches, see 03. 



Pharyngeal bodies. At the entrance to the oesophagus, and immediately below the branchial apparatus, are placed the pharyngeal 

 bones, which produce a second mastication, often more powerful than the first ; for this purpose they are armed with teeth of very 

 variable form and number, according to the species. These bones are usually two inferior, 5ti, and six superior, 02. 



Vertebra: We have already described the general character of the vertebral bones of fishes. Their special forms will be best un- 

 derstood by an inspection of Plate CCXCVII. fig. 1, Nos. 07, 08, 09, with the processes, marked a, b, c. The ribs are shown at 72; 

 the styles or appendages which frequently adhere to those parts, at 73. In a few fishes the ribs are entirely wanting. 



Vertical fins. These are supported by rays composed of an internal portion, named the interspinal, 74, which serves as a sustaining 

 root, by penetrating the flesh among the great lateral muscles, and an external portion, which exhibits the rays properly so called, as 

 seen at 75. We sometimes find an interspinal bone which bears no rays, 70. A certain number of these vertical rays are pointed 

 bones, and are then named spines, or spiny rays ; others are bony or solid only towards their base, their remainder being formed of 

 a multitude of small articulations, and frequently ramified into lesser branches, themselves still further divided ; in these states they 

 are named articulated, soft, or branched rays. Those of the tail, 71, are always soft and articulated ; although, towards the root, both 

 above and below, 78, they gradually diminish till only the solid portion of the base remains. In a great nimiber of fishes the vertebra 

 at which the abdomen terminates and the caudal part begins, and even that which follows it, 83, 83, have a great inferior spinous pro- 

 cess, to which is joined a more or less voluminous bone, 79, extending behind the anus, and thus forming the posterior boundary of 

 the abdominal cavity. 



The sternum does not exist in all fishes. When present, it consists of a series of single bones of various configuration, according 

 to the genera, and at these the ribs terminate. 



Bones of the shoulder and arm. In osseous fishes, we find on each side, immediately behind the orifice of the gills, a suite of bones, 

 forming a kind of frame, on which the opercle rests when closed. These bones, usually attached to the head from above, and unit- 

 ing together below, form an osseous belt, surroumling that part of the body. Their inferior symphysis unites by ligaments to the 

 tail of the hyoid bone (formerly mentioned, 42), and forms with it the ij(/()«;(j, which separates the external openings of the gills from 

 each other beneath, just as the cranium separates them above. This cincture, when complete, is composed on each side of three bones, 

 which represent the shoulder and the arm, to which adheres, posteriorly, a group of two or three others, occupying the place of the 

 fore arm, and bearing the pectoral fin, which may be considered as the hand ; lastly, there is almost always suspended a style, com- 

 posed of one or two bones, which Cuvier regards as the analogue of the coracoidian bone. The highest of these first three bones, 40, 

 is usually forked, and attached by its two crests to the lateral crests of the cranium. It is visible externally at the top of the bran- 

 chial opening, resembling a scale, larger than the others, and is sometimes toothed on its edges. The second, 47, continues along the 

 margin of the branchial opening. The third, 48, always the largest, completes the cincture, by uniting with its counterpart beneath 

 the throat. To the inner surface of the last-mentioned bone adheres a fourth, 51, and fifth, 52, placed one above the other. The 

 free side of these bones bears the pectoral fin, but by means of an intermediate range of four or five small bones, 53. These bonelets 

 may be supposed to represent the carpal series ; and if so, then the two others, 51 and 52, will be the cubitus and radius. The third 



