=Characteristics of Microcephaly.=—(1) Circumference of skull diminished; (2) Brain smaller; (3) Stature small (5 feet); (4) Rarely live to advanced age; (5) Die of tuberculosis; (6) Mostly imbeciles and idiots (few morons). They have their sensory impressions intact and are generally vivacious and muscularly active, even restless. They have good sight and hearing and are highly initiative but have not the ability to any sustained effort. They are actively observant and the majority are affectionate and well behaved. Some are unsteady in walking, others are helpless, and about one-half are subject to epileptic fits. =Mongolian Amentia= (Mongolism).—This type (Kalunk or Tartar variety) received its name from Dr. J. Langdon Down from their facial resemblance to members of the Mongolian race. They number about 5% of all aments including the semi-mongols who have only a few of the characteristics of this type. =Cause.=—Eleven out of twenty-five are from syphilitic origin. Glandular or nutritional defects are suggested as a cause. They will show negative Wassermann test and positive tuberculin tests. Uterine exhaustion and ill health of mother during gestation are factors suspected of entering into this condition. The latter-born of large families are frequently affected. =Pathology of Mongolian Idiocy.=—The brain of the Mongolian ament is considerably under-sized and has less convolutions and is more shallow. The pons, medulla, and cerebellum are about half the size of ordinary feeble minded types. The cells by microscopic examination show an immature condition. This lack of brain development results in deficient expansion of base of skull, hence the characteristic physiognomy. There is no glandular abnormality. =Description of the Mongol Type.=—This type is distinguished by characteristics of skull, eyes and tongue and is usually observed at birth. 1. The skull (Brachycephalous) is rounded and diminished in size particularly through the antero-posterior diameter. The face is flattened, there being no recession of frontal and supra-occipital regions. =Eyes.=—The palpebral fissures are narrow and slope obliquely downward and inward. Lids inflamed. =Tongue= protrudes, is large and marked by large papillæ and scored by transverse fissures due probably to tongue sucking, predisposing to inflammation of the mucous membranes. =Ears= are small and round and have poorly developed and irregular lobules. =Nose= is short and flat and has triangular nostrils. =Teeth= are soft and ill formed and tend to decay. =Hair= is usually scanty and wiry and very dry. =Cheeks= are flushed. Palate is high and narrow and mouth is open, and lips are cracked. Adenoids exist in all cases. =Hands and Feet= are broad and clumsy. Flat foot and knock-knees are common. Skin is rough, coarse and dry. =Abdomen= is large and mushy. Umbilical hernia often present.