. Animal and vegetable physiology considered with reference to natural theology. Natural theology; Physiology; Plant physiology; Biology. 146 THE VITAL FUNCTIONS. 284 rows of teeth are lodged in each jaw ; but only one of these rows projects and is in use at the same time; the rest lying flat, but ready to rise in order to replace those which have been broken or worn down. In some fishes the teeth advance in propor- tion as the jaw lengthens, and as the fore teeth are worn away : in other cases they rise from the sub- stance of the jaw, which presents on its surface an assemblage of teeth in d
. Animal and vegetable physiology considered with reference to natural theology. Natural theology; Physiology; Plant physiology; Biology. 146 THE VITAL FUNCTIONS. 284 rows of teeth are lodged in each jaw ; but only one of these rows projects and is in use at the same time; the rest lying flat, but ready to rise in order to replace those which have been broken or worn down. In some fishes the teeth advance in propor- tion as the jaw lengthens, and as the fore teeth are worn away : in other cases they rise from the sub- stance of the jaw, which presents on its surface an assemblage of teeth in different stages of growth ; so that in this class of animals the greatest variety occurs in the mode of the succession of the teeth. The teeth of the Crocodile, which are sharp- pointed hollow cones, composed of ivory and ena- mel, are renewed by the new tooth (as is shown at A, in Fig. 284), being formed in the cavity of the one (b) which it is to replace, and not being in- closed in any separate cavity of the jaw bone (c). As this new tooth increases in size, it presses against the base of the old one, and entering its cavity, acquires the same conical form; so that, when the latter is shed, it is already in its place, and fit for immediate use. This succession of teeth takes place several times during the life of the animal; so that they are sharp and perfect at all ages. The fangs of serpents are furnished with a recep- tacle at their base for a poisonous liquor, which is squeezed out by the pressure of the tooth, at the moment it inflicts the wound, and conducted along a canal, opening near the extremity of the tooth. Each fang is lodged in a strong bony socket, and. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Roget, Peter Mark, 1779-1869. London : W. Pickering
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