in the Human and Anthropoid Foot. 165 
tubercle at the upper part of the latter surface and close to the 
tibio plantar angle (apex of the pear-shaped facet for caput tali). 
( b ) The epiphysial portion. The part formed from the epi- 
physis is either prismatic or oval in shape, the exact shape depending 
on the presence or absence of a third element of the tuberosity. 
(c) The last and most variable element of the tuberosity is 
the so-called sesamoid bone in the tendon of the tibialis posticus 
which may fuse with the tuberosity. When it is present it 
produces the tuberosity proximally, is somewhat pea-like in shape 
resembling closely the human pisiform bone. It is the presence 
of this element which gives rise to the elongated type of tuberosity ; 
with its absence we have the prismatic type. When this element 
is present there is not infrequently an extension of the surface 
for caput tali on to the tuberosity (facies articularis tuberositatis). 
The single bone which Phitzner describes as tibiale externum 
corresponds in shape and position to the parts described above 
under (6) and (c). It is true that we only get a single separate 
ossicle in this position. In one of my specimens however the 
ossicle was imperfectly bipartite and Phitzner mentions five cases 
in which it was in the same condition. This would suggest the 
view that the single ossicle may consist of both of the above- 
mentioned elements (b) and (c) fused. It may be conjectured 
from the shape of the articular surfaces, or from those of 
coalescence, which element is missing. 
Although therefore as Phitzner maintained, the sesamoid bone 
in the tibialis posticus (tibiale externum, Phitzner) may fuse and 
form part of the tuberosity, it probably only forms the proximal 
portion of the tuberosity, and the occasional bipartite condition of 
the ossicle found here together with the shape of the surfaces of 
articulation or coalescence would suggest that there is another 
element between this sesamoid element aud the apophysial part 
of the tuberosity, viz. that which I have described as the epi- 
physial portion. Bardeleben has shown that there is a separate 
cartilage at the tuberosity up to the second month of foetal life. 
Phitzner, however, apparently would claim this cartilage as the 
same element as his tibiale externum. The matter can only be 
cleared up by the examination of a large number of young tarsal 
bones varying in age, preferably from the fifth to the twenty-fifth 
year. 
BIBLIOGRAPHY. 
Bardeleben. Zur Entwicklung der Fusswurzel. Sitzungsberichte der 
Jenaischen Gesellschaft fur Medicin und Naturwiss. , 1885, 6 Februar. 
S. 27. 
Pfitzner. Beitrage zur Kenntniss des menschlichen Extremitaten- 
skelets. Morphologische Arbeiten hrsg. von G. Schwalbe, Bd. vi. 
1896, S. 245. 
