ERUPTION OF THE PERMANENT TEETH 149 



Sexual differences may be determined in the same manner. The 

 Filipino girls have 1 hyper- to 28 hypo-s; and the Filipino boys 

 have 1 hyper- to 4.6 hypo-s; the German girls have 1 hyper- to 

 7.1 hypo-s, and the German boys have 1 hyper- to 4.3 hypo-s; 

 and the American girls have 1 hyper- to 1.2 hypo-s, and the Amer- 

 ican boys have 1 hyper- to 0.84 hypo-. * 



It is also noticed that the relative number of hyper-s increases 

 with age. This is especially noticeable with the American boys 

 for whom the ratio is 1 hyper- to 3 hypo-s at 8 years of age, and 

 12 hyper-s to 1 hypo- at 16 years of age. 



Hyper-morphism is a condition, of greater age, of development 

 in a certain direction, a male condition, and a condition charac- 

 teristic of the American white. Hypo-morphism is a condition of 

 less age, of development in another direction, a female condition, 

 and a condition characteristic of the Filipino. 



A number of other conditions besides the shape of the head and 

 face characterize the hyper- and the hypo- types, such as the shape 

 of the nose, the relative length of the extremities and of their 

 parts, the ear form, the size of the regions of the head, etc., but 

 it will suffice to give only one of these here, that is, the relative 

 size of the occipital and parietal regions of the head. 



The circumferences of the forehead, frontal, parietal and occipi- 

 tal regions of the head of the school children were taken but they 

 will be reserved for future studies of head form that are at present 

 under way, only the relative size of the occipital and parietal 

 regions of the head to each other will be given here. 



The points selected from which to measure the circmnferences 

 of the regions of the head are the dorsal extremities of the middle 

 roots of the zygoma on each side of the head immediately ven- 

 tral to the external ear, a place that is easily accessible and dis- 

 tinctly felt. The tape was passed from the point on the right 

 side to the point on the left side around the maximum protuber- 

 ance of the parietal and occipital regions of the head, and this 

 distance recorded as the circumference of the part. An index is 

 obtained that is called the occipito-parietal index, by multiply- 

 ing the occipital circumference by 100 and dividing by the pa- 

 rietal circumference. This gives the occipital circumference in 



