290 



RESPIRATION. 



gill-bearing arches are not composed of single 

 undivided curved bones, but of several ele- 

 ments, adjusted with express reference to 

 the elasticity and flexibility of the whole. 

 Six of these arches are primarily developed, 

 and five permanently retained. The first 

 four support gills, the fifth is beset with teeth 

 which guard the opening of the gullet : this 

 latter is termed the pharyngeal arch ; the 

 rest the branchial arches. From the convex 

 side of the branchial arches a double series 

 of interlocking penknife-shaped processes 

 radiate. On the Hat surfaces of these pro- 

 cesses a gorgeous arrangement of mem- 

 branous leaflets is disposed in a transverse 

 manner, each leaflet standing, as already de- 

 scribed, on its edge (jig. 237.). This rich foliage, 

 bearing the complex web of the respiratory 

 capillaries, is itself sustained by a machinery 

 of elastic solid parts, hitherto unknown in 

 comparative anatomy. 



The series of curvilinear bones denomin- 

 nated the arches of the branchiae, and exhi- 

 bited in section at a, fig 237., are inferiorly 

 attached to the sternal chain of bones, pro- 

 ceeding upwards and backwards, and describ- 

 ing a curve, which in different genera varies 

 in decrees of sharpness, and which finally affix 

 themselves by means of ligaments to the base 

 of the cranial bones. These curved bones 

 are constructed of several separable pieces, 

 adjusted with artful reference to the resilient 

 properties of the curvilinear figure. The 

 act of opening the mouth in the fish deter- 

 mines a consecutive series of movements, 

 which end in the preparation of the gills to 

 be traversed by the branchial current. By an 

 appropriate intervening mechanism the move- 

 ments of protruding and retracting the mouth 

 occasion irrespectively the approximation and 

 separation of the branchial processes, accom- 

 panied by an alternate increase and decrease 

 of the curvature of the sustaining arch. The 

 straight penknife-shaped processes (1, 2, 

 jig. 239. .r.), as stated, diverge from the convex- 

 ities of the branchial arches. In nearly ail 

 the osseous fishes, these processes form a 

 double series, the gills being accordingly dis- 

 tinguished as biserial. In those genera in 

 which these processes form a single line the 

 gills are said to be uniserial. In the genera 

 cottus (bull-heads), labroidce (rock-fish or 

 wrasses), sebastes, (Norway haddock), 

 scorpaenidaa (hog-fish), Teidae (John Dory, 

 &c.), the nilotic-fishes, polipterus, gobroidaa 

 (blennies and gobies), lepadogasfidce, a genus 

 of small sucker-fishes), and the cyclopteridas or 

 lump-fishes, may be ranged under one great 

 group, characterised by three biserial and one 

 uniserial gill. The genera sophiidae (angler), 

 batrachoidye, the tetraodons (or globe-fish), 



Owen on Fishes : Rymer Jones's Animal Kingdom ; 

 Article PISCES, in this work, by Prof. R. Jones ; 

 Art. SKELETON, by Mr. Maclise. I wish only here 

 to observe, that the branchial arches appertain to 

 the apparatus of the visceral skeleton, and in antero- 

 posterior order succeed the bvoid arch, on the key- 

 stone of which they are more or less dependant, and 

 the altered configuration, of which they more or less 

 follow. 



the diodons (commonly called the sea porcu- 

 pines), and that curious genus of monop- 

 terus found on the seas of the Molluccas, the 

 gill opening in which is united by transverse 

 partitions of membrane, are characterised by 

 three symmetrical biserial gills. Other le-,s 

 regular genera present other diversities in 

 the disposition of the branchial processes * 

 The penknife-shaped processes (jig. 237.), 

 which radiate from the convexities of the 

 branchial arches are bony in the osseous fishes; 

 but only that part of the solid basis of the 

 process is bony which corresponds with and 

 forms the substance of its blunt or thick 

 margin. In the cartilaginous orders this por- 

 tion is composed of cartilage, the component 

 cells as well as the outline of which are very 

 dissimilar to those of the former class. As in- 

 dicated in the above illustration, that piece 

 in the skeleton of the branchial process which 

 forms the obtuse border exhibits a groove 

 seen sectionally at (b, b, jig. 237.), serving 

 for the lodgement of the processal brunch 

 (g) of the branchial artery. The internal 

 edge of this bony piece is dentated by pro- 

 jecting spines, adapted perfectly to support 



Fig. 238. 



Plan exhibiting the skeletal framework of the lamellae 

 of the gills of Fish in transverse suction. (Ori- 

 ginal.^ 



a, shows the osseo-cai'tilage of the obtuse margin 

 of the lamella, presenting three distinct varieties of 

 component cells, and on the external edge opening 

 into a groove for the lodgment of the branchial 

 artery a', from which, on either side, the ultimate 

 ramuflculi, emptying themselves into the rete mira- 

 bile of the leaflets, may he seen to proceed ; b and 

 c, c', define the beautiful framework which lies pa- 

 rallel with the acute border of the lamella, the 

 lateral processes c, c' stretching on either side along 

 the circumference of the membranous leaflets, pre- 

 venting, by their continuously acting elasticity, 

 the injurious folding of the latter, and, then-tore, 

 the tangling of the respiratory web of capillaries. 

 The extremities of these processes are produced by 

 means of the curled elastic fibres shown in the 

 plan. The dotted lines define the area of the re- 

 spiratory membranous leaflets supporting the ca- 

 pillary network. 



* See Yarrel on British Fishes ; Lecons d'Ana- 

 tomie Comparee, par M. Cuvier ; Owen's Lec- 

 tures on Comparative Anatomy, vol. ii. ; Monro, 

 on the Structure and Physiology of Fishes, 1785 ; 

 Art. Pisc'ics, in this Cyclopaedia; Wagner's Aua- 

 tomy of Vertebrated Animals, by Tulk, 1845. 



