456 



ZOOLOGY 



SECT. 



rad 



of the proximal portion of the shaft is a slight ridge, the deltoid 

 ridge. At the distal end are two articular surfaces, one large and 

 pulley-like trochlea for the ulna; the other smaller capitellum 

 for the radius : laterally are two prominences or condyles, an 

 internal and an external. 



The radius and ulna are firmly fixed together so as to be in- 

 capable of movement, but are not actually ankylosed. The radius 

 articulates proximally with the humerus, distally with the scaphoid 

 and lunar bones of the carpus. The ulna presents on the anterior 

 aspect of its proximal end a deep fossa, the greater sigmoid cavity, 

 for the trochlea of the humerus ; the prominent process on the 

 proximal side of this is the olecranon process. Distally it articulates 

 with the cuneiform. 



The carpal bones (Fig. 1084), nine in number, are all small bones 

 of irregular shape. Eight of these are arranged in two rows a 



proximal and a distal ; the ninth, 

 centrale (cent.), lies between the two 

 rows. The bones of the proximal 

 row are taken in order from the 

 inner to the outer side, scaphoid 

 (sc.), lunar (or semi-lunar) (lun.), 

 cuneiform (cun.), and pisiform. 

 Those of the distal row are, 

 reckoned in the same order, 

 trapezium (trpm.\ trapezoid (trpz.), 

 magnum (mag.), and vmciforni 

 (unc.J- 



The five metacarpals are all 

 small, but relatively narrow and 

 elongated bones, the first being 

 smaller than the rest. Each of 

 the five digits has three phalanges, 

 except the first, which has only 

 two. The distal (ungual) phalanges 

 are grooved dorsally for the attachment of the horny claws. 



The pelvic arch (Fig. 1085) contains the same elements as in the 

 Pigeon, but the union of the ilium with the sacrum is less intimate, 

 the acetabulum is not perforated, and the pubes and ischia of oppo- 

 site sides unite ventrally in a symphysis (sy.}. The three bones of 

 the pelvis ilium, pubis and ischium are separate ossifications in 

 the young Rabbit; but in an adult animal complete fusion takes place 

 between the bones. The ilium and ischium meet in the acetabulum 

 or articular cavity, which they contribute to form, for the head of 



1 The homologies of these bones are not quite certain, but are very probably 

 as follows: scaphoid = radiale, lunar = 1st centrale, cuneiform = intermedium, 

 pisiform = ulnare, centrale = 2nd centrale, trapezium = 1st distale, trapezoid = 2nd 

 distale, magnum = 3rd distale, uncif orm = 4th and 5th distalia. 



FIG. 1084. Lepus cuniculus. Distal 

 end of fore-arm and carpus, dorsal view, 

 the bones partly separated, cent, cen- 

 trale ; cun. cuneiform ; lun. lunar ; 

 mag. magnum ; md. radius ; sc. scap- 

 hoid ; trpz. trapezoid ; trpm. trapezium ; 

 utn. ulna ; unc. unciform ; / V, bases 

 of metacarpals. (After Krause.) 



