360 
On the Sesamoids of the Knee- Joint 
The Rodentia undoubtedly show, however, a greater persistency of the fahellae 
than the Insectivora, and what is more a greater prevalence of cyamella and anterior 
lunulas. Had these been directly searched for by others as well as ourselves, we 
believe their prevalence would have been much more emphasised in the reader's 
mind. The appearance in a few cases of the external posterior lunula is also of much 
suggestiveness. We have not, however, yet come across a case of this lunula co- 
existing with the cyamella* . In the rodents we have further evidence of the 
difference in origin of the two fabellae, partly in the fact that when both are present 
the lateral is larger and more important than the mesial, it being as in man an 
attachment of more than one muscle, and partly in the second fact that, in those 
species which have a single fuhella only, it is invariably the mesial which fails. 
Before we pass to the Edentates as linking up the groups we have already dis- 
cussed we must consider the Primates themselves and ascertain whether they obey 
the same general law, namely that the lower and more primitive forms are multi- 
sesamoidal with regard to their knee-joints, while the higher types have retained 
fewer, or if they exhibit any at all it is only as anomalies. 
(15) Prilnaies. 
We have already discussed Man. The lateral fabella occurs as an anomaly and 
may be either a hemisesamoid or an orthosesamoid. The mesial fabella as an ortho- 
sesamoid has not yet been satisfactorily demonstrated f. It is clearly far rarer than 
the lateral fabella. There is evidence for the cyamella as a very rare anomaly and 
possibly still more rarely of lunulae. The comparative frequency of these anomalous 
sesamoids of the knee-joint in men of different races would be a study of consider- 
able interest and might give valuable hints. It should not be hard by means 
of skiagrams to obtain son;iething like comparative figures for, say, Japanese, 
Negroes;}:, Australians and American Indians which might be set against our 
English work. 
Turning to the Anthropoidea we meet the difficulty so often referred to, namely, 
that the larger skeletons are apt to be too much cleaned for present purposes. 
* The reader will have noted that we have dropped the adjective " lateral" in this latter portion of our 
work. So far we ha^e no evidence heyond Pfitzner's for cats and our own still more doubtful for man 
of the existence of the mesial cyamella even as an anomaly. 
f In 1909 Lunghetti asserted that he had found the mesi&l fabella in two cases, but be does not give 
evidence that tliey were orthosesamoidal, Internationale Monatschrift fiir Anatomie und Phijsiologie, 
Bd. XXVI. S. 71. L. Stieda in 1902 found and exhibited to the German Auatomical Society (Anatomi- 
scher Artzeiger. Verhandlungen der Anatomischen Geselhchafl. Ergiinzungsheft zum Bd. xxi. 1902, S. 127) 
a mesial fabella from a human cadaver. It articulated with the mesial condyle, and was enclosed in the 
knee capsule. It could be clearly seen and felt. Stieda says it was 1 cm. about in diameter, and there- 
fore a very large size for even a lateral fabella. He did not apparently extract the fabella and so make 
himself absolutely certain that it was ossified. He had possibly not fully studied the difiiculties of the 
subject for he describes (S. 128) Heister's figure as "eine sehr gute und lehrreiche Abbildung"! See our 
p. 150 and Plate II. 
{ Chudzinski according to Poirier holds that the sesamoid bone of the inner head of gastrocnemius 
is invariable in the Negro ! We have been unable to verify the reference and very strongly doubt the 
truth of the assertion. Dr E. C. Derry kindly examined for us two negro cadavers in his dissecting room 
and found in both cases neither mesial nor lateral fabellae. 
