As deaf-mute children do not speak so much as normal ones, the restriction of mouth movement might have some effect on the development of the mouth and other parts connected with speach. In 157 deaf-mute boys of 5-21 years of age these parts were measured and compared with those of normal boys. 1. The maximum length and breadth of the head, the ear-head height, the distance between two pupillae, the angle and its breadth of mandible, the mouth breadth and the height of lower mucous membraneous lip of the deaf-mute children are smaller than those of normal ones. But the cephalic index, the height-length index of head, the median angle of closed upper and lower lips, the height of upper mucous membraneous lip, the nasal breadth, the height of the upper and lower mucous membraneous lips, the height of the upper cutaneous lip and the height of the upper lip are larger in the deafmute boys than those of normal children. 2. No significant difference in the percentages of types of incisal occlusion, but the occlusion degree and over-bite degree of incisors of the deaf-mutes are slightly higher than those of the control group. 3. The palates of V-shaped type are more frequent in the deaf-mutes and their height of palate is shallow. The index of palate height, the length of median palatine suture and the length of palatal height are rather small. 4. Among the deaf-mutes the dental arch of parobola type is most frequent, both in the upper and lower jaws. Their length of anterior and posterior dental arch is rather short. Their breadth of anterior dental arch at the canine is normal, but its breadth of the lower jaw and the breadth of posterior dental arch are slightly small. The index of anterior dental arch is smaller than of the posterior in both jaws. The length and girth length of dental arch of the upper jaw are larger than those of the lower and both are smaller than those of the normal.

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