First lesson in zoology : adapted for use in schools . 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. 133 behind and below the gills (see Fig. 139, Ht). Cut away the muscularmasses around the back of the head; expose the cavity of the brain,and remove the loose cellular tissue around the brain. If the gillsof one side are cut away and the intestine drawn out, the dissectionwill appear very much as in Fig. 139. The cavi
First lesson in zoology : adapted for use in schools . 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. 133 behind and below the gills (see Fig. 139, Ht). Cut away the muscularmasses around the back of the head; expose the cavity of the brain,and remove the loose cellular tissue around the brain. If the gillsof one side are cut away and the intestine drawn out, the dissectionwill appear very much as in Fig. 139. The cavity of the mouth widens rapidly, forming behind the bran-chial chamber or pharynx ((?), whence we can pass a probe outwardthrough any of the gill slits. There is a single row of shaip-pointedteeth in front on both the under and upper jaws; in the pharynxabove and below there are rounded teeth. At the side of the pharynxare the four gill-slits and the four arches. The entrance of each slitis guarded in front and behind by a row of projecting tubercles. Wsa. -Anatomy of the brain of the Cunner, dorsal and side view. The ol-factory lobes, the crura, and the thalami not represented. appended to the arches. On the outside of each arch, except thefourth, is a double row of filaments, richly supplied with blood-ves-sels, which, shining through, give a hrilliant red color to the gills; onthe fourth arch there is but a single row. At the upper and posteriorcorner of the pharynx is the small opening of the short branchial chamber has an upward extension on the sides ofwhich lie the false gills (/%), which are accessory respiratory organsnot connected with the gills proper, and receiving their blood supplyfrom distinct arteries. The oesophagus dilates almost immediately to form the stomach(partly concealed in the figure by the liver, Li), which is hardlythicker than the intestine (Jn). This last is of nearly uniform sizethroughout; and after making three or four coils
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1894
