152 ELEMENTARY ANATOMY. [LESS. 



The second is the index. 



The third is the " middle digit." 



The fourth, the " ring digit." 



The fifth the " little digit." 



Each digit consists of three rather elongated bones, termed 

 phalanges, except the pollex, which has but two. 



Each phalanx (like the metacarpals) ossifies by an epiphysis, 

 which is situated at its proximal end. 



In each digit the phalanges become successively shorter 

 and smaller, the third phalanx (or in the pollex the second) 

 being very much smaller than the preceding one, but each 

 being a little expanded at its apex to support the nail. 



10. Extending one's view to OTHER ANIMALS, it may be 

 remarked that man, inasmuch as he possesses limb-bones, re- 

 sembles the great majority of Vertebrates. Still, a vertebrate 

 animal may exist without limbs, as we see not only in the 

 Lancelet, but also in the Lamprey, and even in most Serpents. 



In that man has a pair of upper (or thoracic) and lower 

 (or pelvic) extremities, he again agrees with most of his sub- 

 kingdom. Still, there are many species which only possess a 

 thoracic pair fully developed, as Cetaceans ; or only one pair 

 at all, as the Siren. 



In the construction of the skeleton of the arm and hand, 

 man follows a rule which is universal in so far as the arm- 

 bones are attached to and suspended from a scapula which 

 forms (together with the clavicle when this exists) the root- 

 portion of the limb. For though the root portion may be 

 present without its arm-bones or distal appendages (as in 

 Anguis and others), yet the distal parts are. never present 

 when the limb-root is entirely absent. 



Man agrees with the vast majority of Vertebrates in that 

 this limb-root consists of solid parts (scapula and clavicle) 

 destitute of any direct union with the spine. The limb-root, 

 however, may form a solid girdle, articulated above with 

 the spinous element of the vertebral column, which element 

 alone interrupts the continuity of the solid zone. This 

 is the case, e.g., in Raia clavata. The upper ends of the 

 girdle may not only meet, but overlap, though remaining 

 detached from the spine. This is the case, e.g., in the Toad 

 Dactylethra. The shoulder-girdle may be completed superiorly 

 by being attached to the head through special, interposed 

 bones the supra-clavicle and post-temporal. This is the 

 case in most osseous fishes, e.g. Perch and Cod. 



