xii] Tylosis 219 



A valuable collection of pedigrees illustrating Mendelian 

 descent chiefly of several affections of the skin and hair has 

 been published by Gossage. All the conditions there con- 

 sidered behave as dominants, and respecting several of these 

 the evidence is fairly adequate (132). 



Respecting tylosis palmaris et plantaris the records are 

 especially clear. There is a condition in which the skin of 

 the palms and soles is abnormally thick in varying degrees*. 

 From a study of over thirty family groups affected with 

 this peculiar thickening of the skin it appears that trans- 

 mission was always through affected members except in the 

 case of one family history f. Adding together all the 

 available recorded numbers of children born to affected 

 parents there were 220 affected and 184 unaffected. Since 

 from the nature of such records it is practically certain that 

 affected members of families would be less likely to be 

 missed or forgotten than the unaffected, we may regard 

 these numbers as not an impossible representation of an 

 actual equality. In view of the complete escape of the 

 offspring of the unaffected except in one family tree the fact 

 that tylosis (called also keratosis] almost always behaves 

 as a simple dominant may be regarded as established. 



One family group was unique in the fact that the 

 ancestor first showing the disease came from parents 

 believed not to have had it. This person had a family of 

 12, all affected. In general we know nothing definite as to 

 the origin of such variations, and whether the uniform 



* Compare the famous family of " porcupine-men " often alluded to by 

 the earlier anthropologists. A good account of this family is given by Sir 

 W. Lawrence (Lectures, 1823, p. 385), who remarks : "Let us suppose that 

 the porcupine family had been exiled from human society, and had been 

 obliged to take up their residence in some solitary spot or desert island. By 

 matching with each other, a race would have been produced, more widely 

 different from us in external appearance than the Negro. If they had been 

 discovered at some remote period, our philosophers would have explained to 

 us how the soil, air, or climate, had produced so strange an organization ; 

 or would have demonstrated that they must have sprung from an originally 

 different race ; for who would acknowledge such bristly beings for brothers?" 



t This is the family recorded by Ballantyne, Pediatrics, 1896, i. p. 337. 

 This family was peculiar not only inasmuch as transmission occurred 

 through the unaffected, but also in the fact that the condition appeared 

 in females only. This sex-limitation suggests that the etiology of the 

 condition was in this family distinct from that of the ordinary tylosis. 



