FISH IN GENERAL. 89 



different configurations in different species. The orifice 

 opening from its inferior side into the superior face of the 

 ventricle, is likewise furnished with two valvules, represent- 

 ing the initials in man, but more simply attached. In 

 osseous fishes, the ventricle is most usually of a tetrahedral 

 form ; in the cartilaginous it is rounded and often depressed. 

 It lies beneath the auricle, the cavity turned so as to be 

 almost vertical next the auricle, and horizontal towards the 

 bulb. The coats are very robust, furnished interiorly with 

 powerful fleshy supporters, their substance formed of two 

 very different layers; the internal having fibres more trans- 

 verse, and the external others more longitudinal ; both so 

 little united, that they sometimes cease to be continuous, and 

 appear to form a second ventricle, but this may be a result of 

 incipient decomposition. 



In the bulb of the branchial artery are found the strongest 

 fibres, mostly disposed in a circular manner. It communi- 

 cates with the ventricle by means of two or three membranous 

 valvules ; but in cartilaginous fishes there are often more 

 valves, and sometimes they are of a fleshy nature. The prolon- 

 gation of the bulb passes out of the pericardium, becomes the 

 branchial artery, and penetrates forward beneath the chain 

 of single bonelets that connects the branchial arches. It is 

 soon divided, throwing off a branch to each branchia ; these 

 branches pass along a groove situated on the inside of each 

 arch, more externally than the vein running along the same 

 curve, but in an opposite direction. To the arch a great 

 number of leaflets are attached, in parallel ranges, ordinarily 

 terminated in forked points, often deeply indented. The 

 great branch passing along the arch, gives off a smaller to 

 each of the leaflets, where it bifurcates twice, and spreads 

 into a multitrde of minute vessels, meandering upon the sur- 

 face of each leaflet, until they are finally converted into 

 very small veins. These all terminate in one of the branchial 



