367 



assumed original flipper-like extremity as an individual, which some- 

 times disappears, sometimes remains isolated, and sometimes joins one 

 or another of the adjacent elements. It is of course possible that it 

 may unite itself at once to two other bones between which it lies; 

 but it is not possible, according to this theory, that it should be 

 manifested at the same time as a feature of two distinct bones. 

 Pfitzner^) was brought face to face with this difficulty in the case 

 of the OS hamuli, or what in English we call the hamular process of 

 the unciform. In one place he says that the os hamuli corresponds 

 to (entspricht) the process; but he admits frankly that the process 

 may be very much or very little developed, and that the os hamuli 

 may represent a considerable or a very small part of it; and, most 

 important of all, that invariably the base of the process is a part of 

 the unciform bone. Clearly, if it be true that the os hamuli represents 

 the process, the same element is in two places at once. To avoid this 

 difficulty Pfitzner suggests that the process consists of two parts, a 

 basal one and one forming the free end. He supports this by one or 

 two instances of what might be a line of union between the basal one 

 and the bone, but he admits that the explanation is far from satis- 

 factory, the basal piece never having been seen separate. 



It seems to me that the Vesalianum of both the fifth metacarpal 

 and metatarsal is a similar instance. Pfitzner speaks of that of the 

 metacarpal as representing (darstellend) the tuberosity ; yet, if I 

 mistake not, it has been seen with a very fair tuberosity, and there 

 are immense tuberosities, especially in the foot, in which there is no 

 hint, of the Vesalianum. 



It would seem as if Pfitzner had been somewhat puzzled by the 

 tibiale externum. In his paper on sesamoid bones he wrote as follows : 

 "Alle diese Beobachtungen finden wohl nur dann eine ungezwungene 

 Deutung, wenn man annimmt, daß ein ursprünglich selbständiges 

 Skelettstück bald mit dem Naviculare verschmilzt, um die sogenannte 

 Tuberositas navicularis zu bilden, bald unter den Erscheinungen der 

 Abwanderung abortiert" ^j. Yet in his paper on variations of the 

 skeleton of the foot ^), after saying that an assimilated tibiale externum 



1) Zeitschr. f. Morphol. u. Anthropol., Bd. 2, p. 586. 



2) "All these observations admit of an unforced significance only 

 on the assumption that an originally independent piece of the skeleton 

 sometimes fuses with the scaphoid to form its so-called tuberosity, 

 sometimes disappears apparently by wandering away." Morphologische 

 Arbeiten, Bd. 1. 



3) Morphologische Arbeiten, Bd. 6. 



