HEREDITARY TYPE OF CHARACTER STUDIED. 



51 



3. THE B-TYPE AND THE Bl-TYPE. 



In the general description, as well as in the description of the single 

 cases of brachyphalangy, it has been stated that the anomaly here 

 studied manifests itself in two different somatic types, the B-type 

 (brachyphalangous, shortened) and the B !-type (very brachypha- 

 langous, much shortened). The reasons why this distinction seems 

 indicated may now be discussed. 



It has already been pointed out that in the diagnosis of this char- 

 acter the general aspect of the index fingers, and the distance between 

 the two distal grooves especially might be used as valuable and often 

 fully sufficient diagnostic features. But better than this method of 

 diagnosis by mere inspection is the one based on the objective measure- 

 ments of the phalanges obtained from the radiographs, which are far 

 more trustworthy indices. 



The supposition that we here are dealing with two distinct somatic 

 types of brachyphalangy is confirmed by the analysis of these measure- 

 ments. To be able to estimate from the measure of a certain phalanx 

 whether a shortening is present, it is evidently necessary to have an 

 exact normal standard of comparison. The material here used is 

 obtained from measurements of the hand bones of 301 normal-hand 

 skeletons, given by Pfitzner (1892, 1893) . It needs no explanation that 

 absolute values are useless for our purpose. The point is not whether 

 the questioned phalanx is shorter than the corresponding phalanx of 

 an average normal hand, but whether it is shortened in comparison 

 with the normal finger bones of the same hand. It has, therefore, been 

 necessary to calculate the correlation coefficients between different 

 finger bones in normal hands. 



Based on Pfitzner's material, the correlation coefficients were worked 

 out for the lengths of the first and second phalanx of the index finger (II 1 

 and II 2) of the second phalanx of index and middle finger (II 2 and 

 III 2) and of the second phalanx of the index and ring finger (II 2 

 and IV 2). The values obtained are given in table 2. 



TABLE 2. Coefficient of correlation for lengths of different phalanges, based 

 on Pfitzner 1 s material of skeleton measurements. 



The result shows that there is a very high correlation between the 

 lengths of the second phalanges of the second and ring finger, and the 

 latter measure is therefore used for comparison when estimating 

 whether II 2 is shortened or not. 



