Mr Manners- Smith, A Study of the Navicular. 
161 
A study of the Navicular in the Human and Anthropoid Foot. 
By T. Manners-Smith, M.B., Downing College. (Preliminary 
note.) (Communicated by Professor Macalister.) 
[Read 25 February 1907.] 
Of the bones of the human foot the navicular is perhaps the 
most interesting. For this there are various reasons, morpho- 
logical, mechanical or both. 
The Os Navicular e. 
Facies cirticularis posterior or Astragalar Surface. The whole 
of this surface is occupied by the caput tali and, as a rule, the 
caput is confined to this area. In some cases, however, the caput 
also articulates with the tuberosity (see below). 
The shape of the Facet. The facet for the caput tali is 
generally referred to in English text-books as a large oval, 
concave facet. Phitzner figures two types of surface, a quadri- 
lateral and an egg-shaped, corresponding to the two types of 
ground plan of the navicular, which he describes, i.e. a cuboidal 
and an egg-shaped. 
In none of the specimens examined by me is the astragalar 
facet a perfect oval. It approaches the oval, however, in 33. It 
is egg-shaped in 85. In most cases however (434) it is pear- 
shaped. In the last two varieties the narrow end of the egg or 
pear is directed towards the tuberosity. Sometimes (10) it is 
almost quadrilateral, occasionally (4), triangular. In the re- 
maining cases it was too much damaged to ascertain its exact 
shape. 
According to Phitzner, the difference in the ground form of 
the navicular, and consequently the difference in the shape of the 
surface for the caput tali, depends upon the absence or presence 
of the lateral plantar process or plantar point ; in the first case, 
we have the egg-shaped, in the second, the cuboidal ground plan. 
He states that the projection of this part of the bone must at 
once arouse the suspicion that we are dealing with an inconstant, 
originally independent part of the skeleton, and that this portion 
of the navicular, in reality, is formed by the assimilation of an 
inconstant tarsal, namely, what he calls Cuboides secundarium. 
If this be so, however, we should expect the process to remain 
separate in some cases. In none of the specimens which I 
examined did I find the plantar point existing as a separate 
ossicle, but in one I found a trace of a suture on the facies 
articularis posterior and facies lateralis articularis anterior (cubo 
navicular articulation). The facet for the cuboid was subdivided 
