A FAMILY WITH HEREDITARY (GENOTYPICAU TREMOR 105 



stained from alcohol during that period. Nor have tobacco or coffee 

 had an effect on the tremor. 



As we have seen, tremor has therefore occurred in 4 members of 

 the family, and these are divided among 3 generations. The number 

 of persons in these family-groups that have not been affected by tremor 

 is 5. So then tremor appears in about half of the children. But it 

 should be noted that Viktor N. has not been included among the in- 

 dividuals affected, the genotypical nature of his tremor being proble- 

 matical. Further, the 3 daughters of Matilda K. have not been inclu- 

 ded, since it has not yet been for certain proved whether they have 

 tremor or not. 



As to the fact whether any of the progenitors had tremor or not no 

 information exists. So it may also be suggested that the tremor has 

 appeared for the first time in the family in the person of Magnys N. 

 As is shown by the genealogical tree (fig. 1.) all the offspring of Magnus 

 N.'s unaffected sister are free from tremor. On the whole, children 

 of unaffected parents in this family are always free from tremor. 



As appears from the above the tremor is transmitted as a domi- 

 nant in this family. 



A close examination of the records of hereditary tremor acces- 

 sible in medical literature presents great difficulties. In a number of 

 cases — this applies especially to cases published earlier — the state- 

 ments are not complete enough to admit of a successful inquiry into 

 the nature and mode of descent of the tremor. A study of the published 

 accounts, however, conveys the impression that hereditary tremor has ' 

 been transmitted as a dominant. Thus the affection has been trans- 

 ferred directly from generation to generation. A leap over a normal 

 generation has nevertheless occurred in few cases. In part this 

 circumstance may be explained if we surmise that an apparently nor- 

 mal but in reality slightly affected person oif such a generation has 

 died before his condition was ascertained. The tremor certainly 

 appears at an early period of age as a rule, but in a number of recor- 

 ded cases it has not made its appearence till advanced age. Thus in 

 one case it began at the age of 65 — 70, in some cases at 54, 50, 47, 

 45, 35 or 30. There also exist other possible explanations, but into 

 these I cannot enter now. 



An attempt to fix the ratio of affected individuals to normals in 

 the published accounts of families will show that the affected are far 

 in excess of the normals, but this might probably be due to frequent 



