THE SKELETON 49 
In the carpus of the Mammalia there are usually two additional 
bones developed in the tendons of the flexor muscles, one on each 
side of the carpus, which may be called the radial and ulnar 
sesamoid bones ; the latter, which is the more constant and generally 
larger, is commonly known as the pisiform bone. The fourth and 
fifth carpals of the distal row are always united into a single bone, 
and the centrale is very often absent. As a general rule all the 
other bones are present and distinct, though it not unfrequently 
happens that two may have coalesced to form a single bone, or 
one or more may be altogether suppressed. 
The following table shows the principal names in use for the 
various carpal bones,—those in the second column being the terms 
generally employed by English anatomists :— 
Radiale =Scaphoid = Naviculare. 
Intermedium = Lunar = Semilunare, Lunatum. 
Ulnare = Cuneiform = Triquetrum, Pyramidale. 
Centrale =Central = Intermediwm (Cuvier). 
Carpale1 =Trapezium =Multangulum majus. 
Carpale2 =Trapezoid = Multangulum minus. 
Carpale3 =Magnum = Capitatwm. 
od ani \ =Unciform = Hamatum, Uncinatum. 
Carpale 5 q 
The radial and ulnar sesamoids are regarded by Bardeleben? as 
the rudiments of a prepollex and a postminimus digit ; the primitive 
number of digits being thus supposed to have been seven. These 
bones have been observed in all orders of mammals having five 
complete digits. Occasionally, as in Pedetes caffer, the so-called 
prepollex consists of two bones, of which the distal one bears a 
distinct nail-like horny covering. In Bathyergus maritimus the 
pisiform, or postminimus, is likewise double; the two elements 
being regarded by their describer as representing the carpal and 
metacarpal of the presumed seventh digit. 
Similarly in the posterior limb the tibial sesamoid, and a fibular 
ossification corresponding to the pisiform, are regarded as represent- 
ing a prehallux and a postminimus. 
Metacarpus and Phalanges——The metacarpal bones, with the 
digits which they support, are never more than five in number, and 
are described numerically —first, second, etc., counting from the 
radial towards the ulnar side. The digits are also sometimes named 
(1) the pollex, (2) index, (3) medius, (4) annularis, (5) minimus. 
scaphoid is accordingly also regarded as a second centrale. In the same com- 
munication, Dr. Baur expresses his disbelief in the existence of remnants of a 
prepollex and of a seventh digit in mammals and other vertebrates. (See Anat. 
Anzeiger, vol. iv. pp. 49-52, 1889.) 
1 On the Prepollex and Prehallux, ete., Proc. Zool. Soc. 1889, pp. 259-262. 
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