. A manual of elementary zoology . Zoology. COLD-BLOODED VERTEBRATA 379. micus profundus)—passes below them. The first of these nerves corresponds to the two ophthalmics which are con- spicuous in the dogfish—the ophthalmic branch of the seventh cranial nerve and the (superficial) ophthalmic branch of the fifth—closely united. The deep ophthalmic, which is represented in the dogfish by an inconspicuous twig of the fifth nerve, sends branches to the eyeball and runs on to the snout. Although it appears to arise from the fifth, it is really the dorsal root of the nerve whose ventral root is the
. A manual of elementary zoology . Zoology. COLD-BLOODED VERTEBRATA 379. micus profundus)—passes below them. The first of these nerves corresponds to the two ophthalmics which are con- spicuous in the dogfish—the ophthalmic branch of the seventh cranial nerve and the (superficial) ophthalmic branch of the fifth—closely united. The deep ophthalmic, which is represented in the dogfish by an inconspicuous twig of the fifth nerve, sends branches to the eyeball and runs on to the snout. Although it appears to arise from the fifth, it is really the dorsal root of the nerve whose ventral root is the third (p. 75). The oph- thalmic nerve of the frog is a deep ophthalmic, though the superficial ophthalmic, which does not appear as such, is F^- sections . Fr. .. ' . through gill arches or a perhaps united with it. The ophthalmic of a mammal -divides not far from its origin into a nasal branch, which represents the deep nerve, and a frontal, which may be the superficial nerve. The oph- thalmic branch of the seventh nerve (together with the buccal and external mandibular branches of the same nerve and the lateral line branch of the vagus, which also supply neuromast organs) is lost, with the neuromast organs which it supplies, in the adults of animals higher than fishes. Branches of the lateral line system extend on to the pectoral fins of the skate, and are connected with the exterior by rather long tubules (Fig. 268). The anterior vertebrae are fused into a continuous mass. This, and 25 ugh gil dogfish (on the right) and a cod (on the left), showing how Elasmobranchii and Teleostomi differ in respect of these organs. — From Sedgwick, after R. Hert- wig. Afferent branchial "artery; &, branchial arch of skeleton; bP- and bl1, gill lamellae ; /;, skin of the side of the body between the openings of two gill clefts in the shark; r, cartilaginous gill-ray supporting the septum between two gill pouches in the same; v, efferent branchial arteries, do
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