Karl Pearson and Adelaide G. Davin 
171 
for its patella. Our Plate XIII, Fig. 28 and Plate XIV, Fig. 30 show typical cases 
of such double patellae in man. We suggest that in discussing the pathological 
nature of these cases, the possibility that they have vestigial associations should 
not be entirely overlooked*. 
(7) Bammary of our Knoivledge as to the Sesamoids of the Knee-Joint in Man. 
After 19 centuries of consideration, 18 of which were little better than fumbling, 
we can sum up our present knowledge of these sesamoids as follows : 
(a) An orthosesamoidal lateral fabella occurs in man in about 7°/^ of knee-joints, 
(b) In two to three times this number of cases there is a hemisesamoid, probably 
if indeed not almost definitely a hyaline cartilago. 
(c) The situation of this fabella in about three-fifths of the cases is roughly 
opposed to the articular surface of the condyle near its most posterior point, but 
separated from it by 3 to 7 mms. It is the "Knotenpunkt" of a variety of muscles. 
In about two-fifths of its occurrences the fabella lies on a facet upon the articular 
surface of the condyle. 
{d) There is some evidence for the far rarer existence of a mesial orthosesamoidal 
fabella, but both the evidence and this fabella itself are very elusive. The Collective 
Investigation Report records it in about 1 °/o of knee-joints. Gruber did not find a 
single case in 2340 knee-joints, and we have only found a single and very doubtful 
trace of it in 1 out of 454 skiagrams of the knee-joint. The same Report asserts 
that there are 13 times as many mesial hemisesamoidal fabellae as orthosesamoidal. 
Gruber again, and Pfitzner also, record none whatever. Macalister and Hyrtl and 
others have recorded their presence. 
(e) The lateral cyamella has been reported by Macalister in man. We believe 
that we have found it in under 1 % of skiagrams of the knee-joint. If we interpret 
Gruber's statements correctly, he has erroneously termed the sesamoid he found in 
the popliteal sulcus a fabella, it should be a cyamella, and this is further evidence 
of its rare appearance as an anomaly. 
(/) The existence of a mesial cyamella in man cannot be said to be established 
by the few doubtful skiagrams we have reproduced (Plates X and XI). Mesial 
cyamellae do not occur in any family of mammals universally. Pfitzner reports two 
cases in the cat, which always has a lateral cyamella. The sole interest of the 
anomalous appearance of a mesial fabella would be to strengthen the possibility 
that an organ which is persistent on one side of a limb may anomalously reduplicate 
itself on the other. 
(g) There is some slender evidence of the rare occurrence of lunulae in man. 
They have not as far as we are aware been systematically sought for in the dissecting- 
room. We should expect them as rare anomalies in man as they exist universally 
in certain lower forms. 
* In the Fulham series of skiagrams also occurred four well marked cases of Gruber's Processus supra- 
condyloideus ossis fi-moris : see Pearson and Bell, Monograph on the English Lonyhones, Part I, Tlie 
Femur, Text pp. 85—89, and Atlas, Plates XXVI— LXVIII. 
