The Causes and Prevention of Miners' Nystagmus. 11 



•of my cases have expressed suicidal intentions), are all found in a marked 

 ■case of nystagmus. 



There are two distinct varieties of the disease, in the first of which the 

 symptoms are absent or latent, and the man apparently suffers no disability. 

 In the second group the man suffers more or less disability. Tables I and II, 

 and a number of subsequent tables, are the result of an analysis of 400 con- 

 secutive cases which I have investigated up to the present time. 



Table II. — Analysis of Symptoms. 





361 









305 



Marked 38 



Very marked in 16 





308 



1 - 4 J 







262 









159 



9 





Physical Signs of the Disease. 

 Movements of Eyes. — These, in true miners' nystagmus, are of a rotatory 

 nature, often irregular both in rhythm and extent, increased by exertion and 

 by looking up, and diminished by looking downwards and inwards. The 

 so-called lateral or vertical nystagmus is a rotatory one, with a large lateral 

 or vertical excursion respectively. Both eyes are affected equally in the 

 great majority of cases. I have seen well-marked movement in the stumps 

 of very shrunken and useless eyes (Cases 15, 17). Eate, 80 to 500 a 

 minute (Eomiee (1), 120 to 500). Eange of movement, 1 mm. to 1 cm. 

 (Eomiee (2) ). 



Movements of eyelids. — These are often marked, and, when present, render 

 the detection of the nystagmus very difficult. This sign was present in 

 ■90 cases and marked in 17. 



Tremor of the eyebrows, head, neck, and even of the shoulders, may also be 

 present. Tremor of the head was present in 84 cases and marked in 22. 



Stassen (3) suggests that the head tremor should be looked upon as 

 antagonistic to the ocular movements, and designed to neutralise them. I 

 think it should be regarded as a mark of extension of the disease. There is 

 one very important sign to which sufficient attention has not been paid — the 

 backward and often oblique position in which the head is held. This is 



