Karl Pearson and Adelaide G. Davin 
109 
preparation, and further urging all able to do so to examine carefully skiagrams 
of the knee-joint, recording not only presence but absence of one or both fahellae*. 
The skiagrams give very accurately the position of the fahella with extended 
limb. That position is opposing the middle third of the posterior face of the 
lateral condyle. Generally we may say that while it is sometimes more proximal 
or more distal, it stands midway opposite to the vertical wall of the articular 
surface. As our skiagrams are not stereoscopic it is impossible to hazard any 
statement how far the fahellae are removed from the midplane of the condyle 
towards the lateral border of the articular surface. Our diagrams show what 
great variation there is in the size of these sesamoids. 
In seven of our illustrations (Plates VII, VIII, IX, XV, XVI, Figs. 16, 17, 19, 
20, 32, 33, 34) the fahella shows complete separation from the articular surface of 
the condyle ; it is extremely unlikely that a facet could exist in these cases, and 
certainly not a grooved facet. In possibly three cases only (Plates VIII, IX, XVI, 
Figs. 18, 21, 35) is it reasonable to suppose that fecets may have existed ; in 
these three cases, however, it is hardly reasonable to suggest that the sesamoid 
is in the least depressed below the articular condylar surface. It would thus 
appear that the first of Gruber's positions for the fahella, i.e. embedded in 
the node of fibrous structures, is about, very roughly, two to three times as 
frequent as his second position, i.e. situated in a facet on the condylar articular 
surface. 
Plate XV, Fig. 33 is the case we have already referred to (p. 168) in which 
there is some sign, still very elusive, of a second fahella. We are unable to lay 
any stress on it. It will be at once recognised that the drawings of Trew, Heister 
and Casserius hardly describe anything which appears in our skiagrams. 
We may now draw attention to sesamoids of the knee-joint appearing in some- 
what anomalous positions. Plate XIII, Fig. 29 shows apparently two small 
sesamoids opposing the lateral face of the external condyle, but somewhat 
removed from its surface. Plate XIV, Fig. 31 gives with less certainty a single 
sesamoid in a somewhat similar situation. The roundness of these individuals 
appears to preclude any pathological origin. They are too high up to represent in 
any way normal cyamellae. They might almost be described as intermediates in 
position between cyamella and fahella.. Their almost vertical position over the 
head of the fibula is not without suggestiveness. But without evidence from the 
dissecting-room, or confirmatory skiagraphic records, we wish neither to assert 
that there is a third position possible for the fahella, or that occasionally an 
additional sesamoid of the knee-joint may occur in a position intermediate be- 
tween that of fahella and cyamella. We know of no such sesamoids in lower 
types of life ; for the time being we may call them .■r-sesamoids and if in the 
future no further evidence is forthcoming with regard to them, they may be 
dropped. We did not, however, like to pass them by without a word of record. 
* We shall be extremely grateful for any material with regard to sesamoids of the knee-joiut which 
may be sent to us (Biometric Laboratory, Uni\ersity College, London, W.C. 1). 
