202 ON THE MORPHOLOGICAL CONSTITUTION OF LIMBS. 



limb was connected, and from which it derived its various 

 elements. 



3. The nerves supplied to a limb are not the inferior or 

 haemal di"\dsions of the spinal nerves, but radiating or actinal 

 branches of these divisions. The intercostal nerves are not 

 the nerves serially homologous with the roots of the brachial 

 plexus. The tlioracic nerves, serially homologous witli these 

 roots, are the intercosto-humeral and the succeeding middle 

 intercosto-cutaneous. 



4. Each sclerotome supplying elements to the structure of 

 a limb supplies as a sclerous element a single actinapophysis ; 

 or, as in the rays, an anterior and a posterior — that is, a pair 

 of actinapophyses. 



5. From the structure of the mesial and lateral fin-rays of 

 the fish, the actinapophyseal elements of a limb may be 

 assumed as primordially segmented. 



6. The fin-rays in the fish, and the phalangeal, metacarpal, 

 and metatarsal bones of the higher Vertebrata, are more or 

 less persistent conditions of the distal segments of the pri- 

 mordial actinapophyseal elements of a limb. 



7. By atrophy, or otherwise, one or more of the segments 

 in the successive transverse rows of actinapophyseal elements 

 disappear, so as to leave in man, e. g., four elements in each 

 cai-pal row ; two in the fore-arm, one in the arm, two in 

 the next row for the coracoid and clavicle, one in the proxi- 

 mal row for the scapula. 



8. The nature of the subsequent changes which the ele- 

 ments of the limb undergo, up as far as the shoulder or 

 hip, may be inferred from an examination of the paddle of 

 the Enaliosaur or Cetacean. 



9. A careful apj)lication of the hypothesis to the limb- 

 girdles of the cartilaginous fishes, Amphibia, and reptiles, 

 leaves me strongly inclined to believe that the coracoid is an 

 actinapophyseal segment between the humerus and scapula. 



