108 
On the Sesamoids of the Knee-Joint 
provide of the occasional occurrence of mesial orthosesamoidal fabellae as asserted 
by Hyrtl, Macalister and others. But even assuming the correctness of the obser- 
vation we are forced to the conclusion, that mesial orthosesamoidal fabellae are 
very rare in man, that mesial hemisesamoids are also much rarer than lateral, and 
that generally man confirms the view that there is a marked differentiation 
in origin between the lateral and mesial seasamoids of the knee-joint. 
(6) Skiagraphic Data for the Occurrence of the Sesamoids of the Knee-Joint in 
Man. 
Our data in this case consists of (i) 102 skiagrams of the knee-joint taken at 
a military orthopaedic hospital and examined by the kindness of Dr Stanley 
Melville, and (ii) 352 skiagrams of the knee-joint, which were found among 
the thousands of skiagrams taken at the Fulham Military Hospital and now 
deposited at the Royal College of Surgeons. We owe to the kindness of Professor 
Keith our access to this material. Dr Melville found seven cases of the presence of 
lateral fabellae, we found 22 certain cases and a doubtful four further cases. The 
results 6'9 °/, and 6"2 to 7'4 ° j ^ are in very good agreement. We think it safe 
to conclude that skiagraphically visible fabellae occur in about 7 of human 
cases. If we suppose (i) that hemisesamoids would not show on the skiagrams 
and that (ii) they are twice as numerous as orthosesamoids we should reach about 
21 ° I ^ as the occurrence of the lateral fabella in man, i.e. a percentage approxi- 
mating to Gruber's and that of the Collective Investigation Report, but much in 
excess of Pfitzner's. Dr Stanley Melville, was not able to report a single case 
of the appearance of two fabellae, although there is a shadow on one of his plates 
(see our Plate XV, Fig. 33) which by a great stretch of the imagination might 
possibly be interpreted as a second fabella, much more distally situated than is 
customary. In the skiagrams from the Fulham Military Hospital we have not 
succeeded in finding any trace of a mesial fabella. Yet if the data of the 
Collective Investigation Report are to be trusted we ought to have come across 
five to six mesial orthosesamoids in the total of 454 limbs ; we do not refer to the 
hemisesamoids for we assume they would not appear in skiagrams. Now while 
we cannot disregard the statements of such qualified observers as Hyrtl and 
Macalister, and dogmatically assert with Gruber that a mesial fabella has no 
existence in man, we feel bound to say that we feel it exceedingly elusive, and that 
we must emphasise the importance of the next recorder preserving an anatomical 
If we apply tetrachoric computation to this table — and the variety in size and constitution of the 
fabellae rouyhly justifies it — we find for the correlation 
-1790 ±-0885. 
We see at once that there is no close and significant relation between the appearance or absence of both 
fabellae simultaneously, i.e. there is no close organic relation between them in man. In fact if distri- 
buted purely at random we should anticipate 10 eases in which mesial and lateral fabellae would appear 
simultaneously. We give the numbers which might be anticipated if the appearances were absolutely 
independent in brackets. This approach to independence in origin is certainly singular in the case of 
man, considering the universality of fabellae in so many lower types of life. 
