Degenerative change of the jaw bone is one of the manifestations associated with old age. Although, infrequently, exceptions occur where the physical preservation of the jawbones remains unaltered and in a healthy condition until an advanced age, structural wasting and cellular degeneration predominate overwhelmingly. This process of change from youth to old age and from health to disease generally occurs among lower animals as in man. Although the onset of the wasting of the bone and the morphologic pathology differs among individuals, the portion of the bone affected in most instances, whether man or lower animal, begins with the alveolar process. Alveolar degeneration, as it occurs predominantly in man and perhaps in most animals, excepting sheep, consists, of 2 chief types. These are: 1, atrophy or wasting of the cellular structure in the absence of pus, and 2, suppurative necrosis which destroys the walls and the septi of the tooth sockets. In either instance the breakdown of the alveolus begins at the alveolar crest, gradually reducing the periodontium either to the level of, or below the level of, the root ends. Also, there are instances of localized mechanical injury to the alveolar bone caused by incrustation of calcific deposit or continued packing of food between the teeth. The latter condition becomes more aggravated in the helpless animal, which is unable to remove such an obstruction. Although unlike collections of calculus which may occur at various periods of life of the individual from preadolescence through old age, packing of food between the teeth usually begins during middle or late adulthood. At that period some alteration of the alveolar support of the teeth frequently takes place, detachment of the periodontal membrane from the cementum occurs either partially or totally and the roots of the teeth begin to lose their firm hold in the alveolus. Under the impact of forced pressure during mastication teeth thus affected will yield to the force of the opposing teeth and the food. The resulting space is large enough for food particles to lodge and accumulate. Gradually, with the constantly added food creating separation and more space between the teeth, the shifting of the teeth forms larger pockets for a still greater amount of food to pack firmly thus depressing the gingiva and the affected bone. Especially in the herbivorous animals, the retained grass and twigs aggravated by continued pressure during mastication, produces channeling of the bone in the interspaces of most of the teeth posterior to the canines. Although packing of food results in extensive damage to the alveolar bone between the roots of the teeth of man, the actual destruction seldom proceeds beyond the root ends unless an abscess cavity in the jaw bone results from some other cause.