On tlic Sesamoids of the Knee- Joint 
that the present hypothesis provides no account of the origin of the mesial fahella. 
That is quite true, but it has appeared over and over again in the course of our 
investigation that, whatever the origin of the mesial /a6e/^a, that origin must be 
differentiated from that of the lateral fahella. Not only has the mesial come later 
in most orders and disappeared in the higher types much sooner than the lateral, 
but it is far less significant in size and far rarer as an anomaly. Further, while the 
lateral head of fjastrocnemius in the earlier forms is attached not to the lateral 
condyle but to the head of the fibula, the mesial head retains its association with 
the internal condyle even in the Monotremes. It would demand much further 
study than we have been able at present to give to the mesial fubella to trace 
satisfactorily its origin and the s(jurce of its frequently imperfect condition. We 
would note, however', that if the lateral fahella and cyamella arise from a crested 
filiula, one might seek for a similar origin of the mesial fahella (and the reputed 
mesial cyamella ?) in a like extension of the head of the tibia. Perhaps in this the 
cnemial crest of the tibia in certain birds — the Tuhinares and still more the 
Pygopodes — might be borne in mind*. According to Shufeldt it has (like the 
fibular crest in Platypus) a separate centre of ossification and may be regarded as 
representing the olecranon of the ulna. Vicq d'Azyr as early as 1774, and he was 
followed by Owen, considered the patella itself to be homologous with the 
olecranon f. It is difficult to accept the view of the more modern writers that 
fibular or tibial crests are only extensions of the upper epiphysis of these bones if 
we find they have separate centres of ossification. Still less does it help us to be told 
that the patella is only a sesamoid, unless we hold the view that a sesamoid can be 
produced by some mechanical process when and wherever it is likely to be of 
service I . At any rate if it can be, there seems no r-eason why we should stop at a 
sesamoid — the production of which would be at present as inexplicable as that of 
any new organ, and would require at least an acceptance of Lamarckism to ensure 
its perpetuation. 
Besides the cnemial crest of birds as a vague suggestion^, there is a faint 
possibility of the transfer of a mesial posterior lunula, but we are imable to cite a 
* See W. P. Pycraft, Froc. Zool. Soc. London, 1899, pp. 401 and 1037. 
■]■ " Memoire sur les Kapports ijui se trouvent entre las usages et la structure des quatre extremites 
dans THomme et dans les Quadrupedes," Histoire [et Meiitoires] de V Academie Royale des Sciences, 1774, 
pp. 254 — 270, Pari?, 1778. Vicq d'Azyr associates tibia with the ulna and fibula with the radius. He 
does not, however, claim the association of patella and olecranon to have originated with himself, 
although many later writers have attributed it to him, — "la rotule qui tient lieu d'olecrane comme 
plusieurs anatomistes I'ont demontre " is how he writes on pp. 260 — 261. 
J "I could imagine if further strength were required a sesamoid would be called into being" — as an 
anatomist once wrote to one of the present authors. 
§ There are evidences that the cnemial crest is not a specialised development reached only in a small 
group of birds. Thi s Shufeldt found it as a vestige — disappearing with growth in the young of Centro- 
cercus, and states that in the present state of our knowledge this is incomprehensible, " for in the old and 
mature birds of any of the Grouse the epicnemial crest ia never very prominently produced, nor is it in 
any of their near kin. As age advances this segment becomes thoroughly confluent with the tibia, and 
leaves no trace of its early existence.'' " Osteology of the North American Tetraonidae," Bulletin of the 
U.S. Geological Survey, Vol. vi. p. 344, 1881. 
