Nervous and mental diseases . man skulls ;but the fact is that there are not so many characteristics of race in thecranium as in other parts of the body, and, accordingly, there are stillwide differences of opinion as regards a scientific craniological classifi-cation. Races have been mingling so many thousands of years that 686 MENTAL DISEASES. cranial dissimilarities are the rule among them, even in tribes, and tosome extent in families. These diversities of form have been designatedas dolichocephalic, mesocephalic, and brachycephalic—words whichmerely convey an idea of the relation of the l
Nervous and mental diseases . man skulls ;but the fact is that there are not so many characteristics of race in thecranium as in other parts of the body, and, accordingly, there are stillwide differences of opinion as regards a scientific craniological classifi-cation. Races have been mingling so many thousands of years that 686 MENTAL DISEASES. cranial dissimilarities are the rule among them, even in tribes, and tosome extent in families. These diversities of form have been designatedas dolichocephalic, mesocephalic, and brachycephalic—words whichmerely convey an idea of the relation of the length to the breadth ofthe skull when viewed from above. The anteroposterior is to thebiparietal diameter as 100 is to x, is the formula for determining this cephalic index. All length-breadth indices below 78 are considereddolichocephalic ; from 78 to 80, mesocephalic; and above 80, brachy-cephalic. We may assume that the physiological limits of this indexare 70 to 90. This is based upon thousands of measurements of skulls. Fig. 269. by various investigators. Any excess or diminution of these figuresmust hence be regarded as pathological (Fig. 269). But while one skull may be narrower or broader than another, thereis compensation in other diameters. The dolichocephalic has a greatervertical diameter, for instance, than the brachycephalic skull. Besides these characteristics, something must be said regarding thephysiological asymmetry of the skull. The fact that the arms and handsare not symmetrical on the two sides of the body, either in size or func-tion ; that the legs and feet are not symmetrical; that the left cerebralhemisphere is larger and more complicated than the right, would natu-rally lead us to anticipate some slight asymmetry of the two sides of theskull, and the facts of observation support us in the statement that asym-metry is the rule and perfect symmetry the exception. More than athousand postmortem examinations, the examination of several hundredheads, and
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