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The influence of properties of the diets on the retardation of growth of the jaw bones and masticatory muscles has been established. As the intake of liquid foodstuffs increases in the human diet, it is considered possible that these liquid diets may retard the growth of human salivary glands. 180 newborn C3H/He strain male mice were divided into solid and liquid diet groups and then the development and aging of the submandibular glands were observed both in function and morphologically until 60 weeks of age. The following results were obtained: 1. No differences could be detected in body length and body weight of the mice between solid and liquid diet groups. The wet weight of the liver in the liquid diet group was significantly larger than the solid diet group, which suggested that the liquid diet may have accelerated metabolic functions. Additionally, masticatory muscles of the liquid diet group were significantly smaller than the solid diet group which suggested growth retardation of the masticatory organ. 2. The submandibular gland wet weight and its DNA content in the liquid diet group were lower than in the solid diet group during the experimental period. This suggested that the number of cells and their ability to divide was diminished. The wet weight of glands per unit DNA content showed an increase in cell size during the adult period. 3. The alpha-amylase activity and total protein content of the submandibular glands in the liquid diet group were lower than in the solid diet group. This suggested that the saliva secretory function and protein synthesis were depressed, in agreement with the low number of cells detected. 4. The differentiation of the acinar cells and convoluted tubule cells of the liquid diet group was retarded and the 60 weeks subgroup showed hypertrophy of the convoluted tubule cells, disappearance of the secretory granules and a decrease in the number of acinar cells. 5. Slight stromal fibrosis was observed with increasing age (60 weeks) with no difference between the two groups. 6. This suggested that when mice were fed a liquid diet, the development of salivary glands was retarded and also aging changes occurred more rapidly.