First lesson in zoology : adapted for use in schools . 132 FIRST LESSONS IN ZOOLO&Y. arches of the spinous processes, the passage being called theneural canal, and is thus preserved from injury by thestrong arch-work over it. But the brain must be preservedfrom harm, and the jaws need a firm, bony support. Hencewe have a skull formed of numerous more or less movablebones, in the upper and back part of which is the brain-cavity, communicating in front with the orbits or eye-cavityand the nasal cavity. In front are the bones of the upper and lower jaws; be-hind are the four opercular bones; and
First lesson in zoology : adapted for use in schools . 132 FIRST LESSONS IN ZOOLO&Y. arches of the spinous processes, the passage being called theneural canal, and is thus preserved from injury by thestrong arch-work over it. But the brain must be preservedfrom harm, and the jaws need a firm, bony support. Hencewe have a skull formed of numerous more or less movablebones, in the upper and back part of which is the brain-cavity, communicating in front with the orbits or eye-cavityand the nasal cavity. In front are the bones of the upper and lower jaws; be-hind are the four opercular bones; and below, at the base ofthe lower jaw, the tongue-bones, while the pectoral and. Fio. 139.—Anatomy of the Cunner, male, i, lateral line; Ht, heart; C. pharynx;Ps, pseudo-branchia; Sp, spleen; .s, aii-bladder; Ki^ Ki\ kidney; hi, bladder;T, testis; A, aorta; B, bram; In, intestine; Li, liver; O, gills. ventral fins are more or less connected by muscles and ten-dons to the base of the skull. The bones are small and ex-ceedingly numerous, a number of small bones forming theskull and supporting the fins, so that we may in a singlefish count upwards of five hundred separate bones. To dissect a percli or cunner the side-wall of the mouth must be re-moved, then the gill-cover; study the arrangement of the gills. Nextmake an incision along the median ventral line from the level of thepectoral fins to just before the anus, and following the upper edge ofthe body-cavity upward and forward, cut away the body wall, takingcare not to injure the large swimming bladder above, nor the heartin front, Now open the pericardial cavity, which lies immediately ANIMALS WITH A BACKBONE
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1894
