60 Hereditary Syndactylism and Polydaetylism 



the condition ; also 6 toes on each foot from which the extra toe had 

 been removed by operation. 



V. 5. Dora, aet. 1 year. Webbed 3rd and 4th fingers on each 

 hand. Feet normal. 



Skiagraph J (Plate XIX). Right Hand. Here the phalanges of the 

 3rd and 4th fingers are normal in shaj)e and size but lying between 

 them are three bones which are evidently the bony basis of an extra 

 digit. The terminal phalanx of this extra digit is in close association 

 but distinct from the terminal phalanges of the 3rd and 4th fingers. 

 The middle bone lies in close association with the proximal phalanx of 

 the 4th finger and middle phalanx of the 3rd. The proximal bone is 

 smaller, lies between the heads of the 3rd and 4th metacarpals. There 

 is crooking of the little finger. 



Left Hand. The phalanges of the 3rd finger are normal in size and 

 shape. In the 4th finger, the proximal phalanx is represented by tri- 

 angular-shaped bone, and towards the head of the 4th metacarpal is a 

 distinct centre of ossification. Between this triangular bone and the 

 proximal phalanx of the 3rd finger and close to its base lies a third 

 piece of bone. 



The middle phalanx is normal in shape and size and the terminal 

 phalanx is in association with the middle phalanx of the 3rd finger. 

 The little finger is crooked. This is probably the most interesting of 

 the series of skiagraphs not only as showing the condition of the de- 

 formity in the 5th generation but also giving evidence explaining the 

 deformities in the older relatives. 



Discussion. 



In this pedigree the digital abnormality, whether it be in the form 

 of syndactyly or Polydactyly or both, appears as a dominant. It only 

 appears in the offspring of an affected parent and either sex may 

 transmit. The offspring of unaffected parents are always free from it. 



In comparing the affected families it will be seen that in only one 

 are all the members aftected — II. 2— II. 10. Now it is more than likely 

 that the mother of this family I. 2 was normal. Had she been affected 

 the tradition would have been preserved in the family. If this be 

 assumed then it follows as an inference of strong probability that I. 1 

 was a pure dominant to the condition and that the offspring of this 

 union were impure dominants DR to the condition. Of course the 



