366 
On the Sesamoids of the Knee Joint 
we see' their great importance. The non-appearance of the lunulae in the mar- 
mosets is more or less accounted for, because in the lower stage of the lemuroids 
while they are found, they are not universal ; the lunulae have already begun to 
disappear, although the type lemuroid may be said to be that which has both 
fahellae, the cyamella and the lateral anterior lunula. A further point which will 
develop its interest as we proceed is that noted by Owen in the Aye-Aye, namely 
the situation of the cyamella. We reproduce, Plate XXVIII, Fig. 74 6, Owen's 
drawing. The reader will note how in a marvellous manner the cyamella and the 
lateral fabella are being brought into close association. The bearing of this on 
the origin of both of them will be seen in the sequel. The cyamella articulates 
with the head of the fibula and the possibility of the lateral fabella articulating 
with the cyamella is seen to exist*. Fig. 74 a shows our actual dissection ; the head 
of the fibula h is in contact with the cyamella f. The two branches of gastro- 
cnemius a and h have been deflected to show the fabellae c and d, as dark patches ; 
the positions in which they rest on the condyles are also indicated. 
Plate XXVIII, Fig. 77 gives the dissection of the knee-joint of Indris brevi- 
caudata and shows the fabellae and cyamella in position. 
Plate XXVII, Figs. 70 a and 70 b show in Lemur varia the type knee-joint of 
the lemurs, a is the external, b the internal fabella, c the cyamella on the head of 
the fibula and d is the lateral anterior lunula. Figs. 75 and 73 show with the same 
notation the same four sesamoids in L. catta and L. melanocephalus. 
Plate XXVIII, Fig. 76 gives the lateral aspect of the dried knee-joint of Pero- 
dicticus potto. In this case no fabellae were present, having most probably been 
knocked off. The cyamella (cy.) is seen resting on the head of the fibula, the popliteal 
tendon sends a branch down to the head of the fibula. On the posterior and 
upper face the cyamella is concave, and this hollow seems designed for the fabella 
to rest in. The anterior external lunula is in its usual position, i.e. in the semi-lunar 
cartilage just in front of the popliteal tendon. 
The main point of interest in the lemuroids is undoubtedly the link that the 
lumda presents with the Rodents and Insectivores. But the close relationship which 
the forms and positions of cyamella and lateral fabella in the lemuroids bear to a 
continuous articulating system connecting the head of the fibula with the lateral 
condyle of the femur is full of suggestiveness. This relationship of lateral fabella 
and cyamella explains we think to some extent Gruber's confusion of the two when 
as in man only one occurs and then as an anomaly. 
(16) Edentates. 
Before we discuss the very peculiar sesamoidal knee-joint characters of this 
order it seerns desirable to be clear on a point which is rather obscure in some of 
the earlier writers, who are liable to confuse the cyamella with the lateral fabella. 
* It is worth while comparing the drawing of the cat's knee-joint on our p. 352 with Owen's of the 
Aye-Aye's knee-joint. The manner in which with flexed limb the lateral fabella and cyamella come in 
contact will be obvious. 
