Heredity of the Sensor ial Qualities. 39 



on anaesthesia or hyper-sesthesia of the nervous element All 

 anomalies are transmissible by heredity. 



i. The peculiarities of vision which depend on mechanical 

 causes are strabismus, myopia, and presbyopia The transmission 

 of these is very common. In general, it is to hereditary causes 

 that we are indebted for the conformation of our visual apparatus, 

 and, consequently, for our being far or near-sighted. 



Portal, in his Considerations sur les Maladies de Famille^ de- 

 scribes an imperfect form of strabismus, called the Montmorency 

 sight, with which nearly all the members of that family were 

 affected. 



Danvin observed that the Fuegians, when on board his ship, 

 could see distant objects far more distinctly than the English j 

 sailors, notwithstanding their long practice. 1 This is clearly an 

 acquired faculty, accumulated and fixed by heredity. 



One of the most striking cases of heredity of vision is the ever 

 increasing number of the myopic among persons given to in- 

 tellectual work. According to M. Giraud Teulon, continual 

 application with the eyes near the object is the great cause of 

 myopia.* Professor Bonders, of Utrecht, while studying the 

 statistical reports, was surprised to find that myopia is a disease of 

 the wealthy classes, and that the inhabitants of cities are specially 

 liable to it, while those of the country are almost exempt. In 

 France the Conseils de Revision have noticed the same fact In 

 England, at the Chelsea Military School, among 1,300 boys only 

 three were myopic. In the Universities of Oxford and Cambridge, 

 however, the number of myopic subjects was considerable at 

 Oxford 32 in 127. In Germany the results are even more 

 decisive. Dr. Colin, of Breslau, undertook the task of examining, 

 in the schools of his own country, the eyes of 10,000 scholars or 

 students. Among these he found 1,004 myopic about ten per 

 cent In village schools they are not numerous only a quarter 

 per cent. In the town schools the number of the myopic increases 

 with the grade primary schools it is 67; middle schools, 10-3; 

 normal schools, 197 ; gymnasia and universities 26^2 per cent 



1 Variation, etc., ii. p. 223. 



* Rev ue (fes Cour; Scientifiques. 3 Sept. 1870. 



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