A FAMILY WITH HEREDITARY (GENOTYPICAL) TREMOR 99 



of certain groups of muscles. In the case of hereditary tremor as has 

 already been mentioned, tremor is the only, or at least the chief symp- 

 tom. So we can say that the symptomatology of hereditary tremor is 

 exceedingly simple. But the tremor is able to great variation. 



The tremor is usually restricted to the arms and the hands, but 

 it sometimes also appears in the head, and may then make speech 

 difficult. Tremor is also found in the legs, sometimes it extends over 

 the whole body, perhaps with the exception of the head. It is often 

 predominant in one side of the body, e. g. in the right arm and hand. 



Hereditary tremor may occur at any time of life, though most fre- 

 quently it appears in early youth. It often increases in intensity and 

 extension as years go by, sometimes it decreases or remains the same, 

 but a return to perfect health is very seldom seen. The tremor is usually 

 present without intermissic n, yet it generally ceases during sleep and 

 perfect rest. On the other hand, motion and exertion make it increase 

 in intensity and may cause it to assume the nature of intention 

 tremor. Less frequently the tremor presents itself exclusively in con- 

 nection with bodily exertions or emotions, being quite absent in the 

 intervals. Sometimes the trembling may be suppressed for a little 

 while. Thus in the literature we hear of a man affected with tremor 

 who was a good shot when the main thing was to take aim and shoot 

 quickly. A couple of watchmakers with hereditary tremor are also 

 mentioned in the literature. 



The tremor may be rather rapid (with 8 — 10 vibrations a second) 

 or comparatively slow (with 3 — 4 vibrations a second). As a rule we 

 find a rapid, fine-waved tremor which, however, as a result of strain 

 or emotion may pass over into a more large-waved one. 



When favourably localized and having little intensity the tremor 

 need not be a hindrance to the affected person in his work, but some- 

 times it may make him an invalid. Considerable difficulty in eating 

 and drinking may arise. The handwriting, which may sometimes be 

 good, is generally rough and may be perfectly illegible. Through tre- 

 mor in the lingual and pharyngeal muscles, speech is liable to become 

 highly indistinct. 



Persons affected with hereditary tremor are often nervous people 

 possessed of an unstable emotional life. Sometimes, in addition to 

 tremor, they also present increased reflexes and symptoms of motor 

 irritability. Nervous diseases seldom coexist with tremor. 



The anatomical basis of hereditary tremor is unknown. So far 

 only one case has come to postmortal examination, but it has not been 



