Karl Pearson and Adelaide G. Davin 
159 
small prefigaration of it had been ejected in the sectioning as one or two cavities 
were visible in the section. Either alternative is possible as the nodule is much 
harder than its environment and the knife may slip on it, and again, not only is the 
mesial fabella not infrequently absent in the cat, but it develops far less rapidly 
than the lateral. 
(ii) We asked Professor Elliot Smith if he could provide any information as to 
the origin of sesamoids in general from a human foetus. The fabella and ct/amella 
not being universal in man the patella and a raetatarsial sesamoid were selected. 
He placed the matter in the hands of Mr R. B. Green, who has most kindly sent us 
the accompanying report. 
yVo(!e 071 the Histology of Sesamoids in the full-term human Foetus. 
Longitudinal sections throngh the developing sesamoid bone in the tendon of the Flexor hrevis 
Hallucis .show the cartilage to be essentially of the hyaline variety. At the periphery of the 
cartilaginous nodule a narrow transition zone between the cartilage and the surrounding young 
connective tissue may be seen. In this zone fine fibres are interspersed in and gradually fade away 
into the hyaline matrix. Other fibres pass round the periphery of the cartilage from one extremity 
to the other. 
Longitudinal sections of the patella in the full-term foetus show a similar arrangement 
in which those fibres which are a continuation of the proximal to the distal tendinous attachment 
on the surface of the cartilage are more marked. 
It will thus be seen that independent lines of investigation confirm Gruber's 
statement and there is little doubt that if it holds from cat to man, we are fairly 
safe in asserting that sesamoids are always prefigured by hyaline cartilage*. 
The importance of this conclusion is very great. If sesamoids are always pre- 
figured by hyaline cartilage, and do not appear without this origin, and further if 
this origin can be detected in the foetal state, it is clear that the presence or absence 
of hyaline cartilage in the foetal state is the condition for the presence or absence of 
either hemisesamoid or orthosesamoid ; and the theory that they are produced by 
intensive stress or friction falls to the ground, unless it, indeed, be asserted that 
such factors have produced antenatally the hyaline cartilage nodule ! Unless fibrous 
cartilage could first be converted by stress into hyaline, it is hopeless to maintain 
that such stress could produce sesamoids. But a study of the regions intermediate 
between fibrous and hyaline cartilaginous areas appears to indicate that, while there 
is a form of cartilage which is neither and yet may become either, the one is not an 
antecedent of the other. In our Plates XVII, XVIII are shown (i) the section of 
the kitten's cyamella and the enlargement of the hyaline cartilage, (ii) the section 
of the kitten's lateral fabella, (iii) the section of the metatarsial sesamoid in the 
human foetus and (iv) the section of the foetal human jxdella. A more complete 
study of such material would we believe be of great interest. At present we are 
only concerned with the fact that the master-craftsman was correct and the text- 
book writers, who still cling to mediaeval traditions and hypotheses, are wi'ong. 
* Since the above words were written, we have been able to confirm Gruber's statement in the case 
of the dog, the rabbit, and otlier mammals. The results will be discussed in the next instalment of this 
memoir. 
