Had the larger teeth been implanted in the inferior maxillary bone, the labour imposed would have been much augmented, and the end attained have been in no way expedited. 21. _Provision has been made by Nature to meet the wear to which the horse's teeth are subjected._ Such provision, however, I am of opinion, has been somewhat mis-stated by the majority of writers who have treated of this matter. Many of these authors dwell greatly upon the growth of the teeth of the horse, as though this function were in constant activity during the life of the animal. The arguments by which their views are supported, are primarily drawn from analogy rather than deduced from observation. Because the teeth of certain animals, especially those classed by naturalists as rodentia, and of which the rat and rabbit are familiar types--because the teeth of these creatures are known to grow, and those of the elephant are also proved to increase--the same is assumed of the horse. The inference is certainly of strength, but nevertheless it is far short of proof; a similarity between the animals is not demonstrated, and a sameness cannot be shown. Moreover, in another direction, an evidence is attempted to be made of the consequence which ensues when one of the molar teeth loses its vitality; the tooth that so suffers is rapidly worn down, and the opposing tooth becomes of an unnatural length, projecting far beyond its fellows. The increase of length in such a case has been supposed to go on in the sound organ at the natural rate, and the growth of the diseased tooth only has been thought to be stopped; hence the amount of wear and of growth is attempted to be measured; but on consideration it will be seen, that something more than the mere cessation of increase has to be calculated. The carious tooth had ceased to be a part of the living body, and with its vitality the organ lost its capability of self-preservation. The condition of the part had changed, and of the strength which vitality bestows, all persons must be conscious. To argue from the results produced upon dead matter, and then apply the deductions to living organs, is a course which no physiologist will sanction. The tooth that had ceased to live, might be quickly worn down, for other reasons than that it had ceased to grow. This is so clear, and the inference to which allusion was formerly made so obviously untenable, that I shall not longer detain the reader by dwelling upon either, but proceed to state my own views of the subject. I admit the teeth of the horse do grow, and only doubt if the process has been properly described. When the crown of the tooth first appears in the mouth, the fang is not completed, and the root has not even been developed. The horse is seven years old before all the roots are perfected, and when these are completed, I doubt if the after growth is material. If the jaw of an old horse be examined, the alveolar cavities