46 



ANATOMY AND PHYSIOLOGY OF 



trapezium is situated in the posterior part 

 of the carpus, and presents two smooth sur- 

 faces for articulation with tlie ossa cunei- 

 forme and brachii. Its external, lateral sur- 

 face is convex ; its internal concave ; its 

 superior border gives attachment to the 

 flexores metacarpi ; and into the inferior is 

 inserted a ligament. The ossa pisaformoe 

 — for sometimes there are two present — is 

 situated posterior to the trapezoides ; its 

 form is orbicular or pea-shape. 



METACARPAL BONES. 



The metacarpal bones are three in num- 

 ber, viz : metacarpus magnum, 1 ; metacar- 

 pus parvum, 2. There seems, however, so 

 great a disproportion between the os mag- 

 num and ossa parva, that the former may 

 be considered as the principal support of 

 the fore extremities. 



Q. What is the situation of the metacar- 

 pus ? — A. Immediately beneath the carpus. 



Q. Describe the form of the metacarpi 

 magnum. — A. It is a long cylindrical 

 bone, presenting on its anterior surface a 

 circular, smooth appearance ; its posterior 

 surface is somewhat flattened and depressed. 



Q. How is the bone divided ? — A. Into 

 a body, and two extremities. 



Q. Describe the extremities. — A. The 

 superior presents a smooth articulatory sur- 

 face, tapering towards its outer edges, yet 

 more depressed on its inner and posterior 

 part ; in the anterior region is a roughened 

 prominence, for the insertion of the extensor 

 metacarpi, and on the lateral side of the 

 bone are eminences which afford insertion 

 for the lateral ligaments. The inferior ex- 

 tremity presents a pulley-like surface, with 

 two unequal condyloid surfaces, separated 

 by a semi-circular eminence, which corre- 

 sponds to a counterpart found on the supe- 

 rior end of the suffraginis. 



Q. What are the articulations of the 

 metacarpi magnum ? — A. It articulates su- 

 periorly with the carpus ; inferiorly, with the 

 OS suffraginis ; posteriorly and laterally, with 

 the ossa sqoamoidea, and metacarpi parva. 



OSSA METACARPI PARVA (sPLENT BONES). 



Q. How many bones compose the ossa 



metacarpi parva ? — A. Two : external and 

 internal. 



Q. Describe their situation. — A. They 

 are attached to the lateral and posterior 

 parts of the metacarpi magnum. 



Q. How do you divide them ? — A. Into 

 bases, middles, and apices. 



Q. Describe the base. — A. It is sur- 

 mounted by a smooth articulatory surface, 

 corresponding to the inferior portion of a 

 part of the knee joint. 



Q. Describe the middle. — A. It is tri- 

 facial : the anterior surface is roughened 

 for the insertion of inter-articular tissue, 

 which connects it with the cannon ; the inner 

 surface is excavated; the outer surface is 

 rounding, and terminates, posteriorly, acu- 

 minately. 



Q. Describe the apex. — A. It tapers, and 

 ends in a tubercle, which curvates in an 

 inferior and superior direction. 



Q. How do the ossa metacarpi parva 

 differ ? — A. The external is generally larger 

 than the internal, and has a broader articu- 

 latory surface. 



Q. What^one does the external splent 

 articulate with ? — A. The unciform. 



Q. What bone does the internal splent 

 articulate with ? — A. The trapezoid. 



Q. How are the splents connected to the 

 cannon ? — A. By cartilago-ligamentous tis- 

 sue. 



Q. What changes does this cartilaginous 

 tissue undergo, subsequent to adult life ? — 

 A. In a majority of cases it becomes ossified. 



PASTERN BONE (oS SUFFRAGINIs). 



Q. Describe the location of this bone. — 

 A. It is located beneath the cannon, and 

 takes an oblique direction from the same ; 

 it articulates superiorly with the cannon; 

 posteriorly with the ossa sesamoidea. 



Q. Describe the form of the os suffra- 

 ginis. — A. It is a flattened cylinder, yet its 

 superior portion is more bullcy than the in- 

 ferior ; it is generally considered as being 

 about one-third the length of the cannon, 

 and is divided into a body, superior and 

 inferior extremities. 



Q. Describe the body of the os suffra- 



