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POPULAR SCIENCE MONTHLY. 



for the results of their observations in their own countries in regard 

 to all classes of people. He at length published a symposium of the 

 answers showing the prevalence of trachoma in different countries and 

 among the different classes of people. As given in this contribution 

 there seemed to be a confused accumulation of facts which had, on the 

 whole, apparently little meaning. Peoples of contiguous countries, of 

 the same color and not very different in habits of life, were reported as 

 differing widely in respect to the prevalence of the affection. Ko 

 reasons were assigned and none seemed to be suggested by the varying 

 facts. An analysis which I made of this report showed that among 

 peoples with the 'medium' or tall heads, like the Irish and the Italians, 

 trachoma is rife; while among peoples with the broad head, like the 

 Bavarians, or with the long head, like the negroes whose ancestors 

 were from the West or Guinea coast of Africa, trachoma did not pre- 

 vail ; but it is interesting to note that descendants of the negroes of the 

 northern part of Africa, where the heads of the natives are often tall, 

 are subject to trachoma equally with the whites among whom they live. 

 I have in another connection discussed this question at more length.* 



A glance at Fig 14 will show that the negro 

 as he is known in our Southern States not only 

 throws the head backward in the manner char- 

 acteristic of the long head, the strong facial 

 angle and the depressed visual plane, but that 

 the eyebrows are characteristically elevated. 

 This drawing up of the brow is accompanied 

 with a drawing upon the lids and hence no 

 pressure is brought upon the surface of the 

 eyes by the upper lids. In the case of the tall 

 head with the high plane of vision the brows 

 are strongly compressed and the lids bind 

 upon the eyeball and thus in the midst of dust 

 and filth or even in good sanitary surround- 

 ings disease of the lids may be promoted. 

 Eeverting once more to the declinations of the retinal meridians, 

 the same effect may be induced both as to the pose of the head and the 

 relaxed state of the lids. It is, however, impracticable to consider the 

 subject from that point of view at present. 



Turning to a larger and more important subject, the negro is 

 known to be especially subject to tubercular diseases, yet he is, to an 

 unusual degree, immune from consumption. In my investigations 

 during the past few years, I have not seen a consumptive the direction 

 of whose visual plane was not much higher than the standard. We 

 shall come to this from another point of view. It is easy to see that 

 * 'Transactions of the British Medical Association,' 1897. 



Fig. 14. The Long Head with 

 Pkognathous Face. Fa- 

 cial ANGLE +15°. 



