262 PROFESSOR OWEN ON THE GENUS DINORNIS. 



two fibulse ; the humerus and radius are usually, and the ulna is always, longer and larger 

 than their analogues in the hind extremities ; then also there are the two distinct carpal 

 bones, a metacarpus and characteristically modified phalanges. The chances were thus 

 greater that the next bone of an extremity discovered in the alluvium of New Zealand 

 would have been one of the anterior members, had these been developed to serve as 

 wings in the Dinornis. But what is the fact ? Eighteen femora, eleven tibia and six 

 tarso-metatarsi, with two toe-phalanges, have been consecutively discovered, and not a 

 trace of any part of the osseous framework of a wing : not a fragment of scapula, of hu- 

 merus, or of the bones of the forearm or hand. 



The doctrine of chances thus adds its proof, were such required, to the inferences of 

 physiological correlation, that the Dinornis had no wings. We may next inquire to 

 what extent, short of the faculty of flight, the anterior or pectoral members were deve- 

 loped in this extinct genus, with the same confidence in the laws of correlation as a 

 guide to the determination of this question. 



The anterior members present very diiferent degrees of arrested development in the 

 different existing species of the Struthionida , and always retain, under even their most 

 rudimental condition, the characteristic modifications of form and structure by which 

 they are adapted to serve the ofiice of flight in ordinary birds. 



In these, as is well known, the body is made specifically hghter, and in a direct 

 ratio with the powers of flight, by a proportionate extension of the air-cells through the 

 muscular and osseous systems. A much greater proportion of the skeleton is permeated 

 by air in the Swallow than in the Quail. 



The Rhea and the Ostrich have the largest and most wing-like anterior members of 

 all the Struthionida ; they use them to aid in their swift progression : throwing their 

 body forwards beyond the centre of support afforded by the hind legs, they partly sustain 

 it by the flapping of the curtailed wings, whilst the legs, to the extent to which they are 

 thus relieved from the act of sustaining, are free to exert additional force in propelling 

 the body : and it may be said of the Ostrich at full speed that half the body flies and 

 half runs. Now we find that in these semivolant StrutMonidce the warm and expanded 

 air of the respiratory cavities is freely admitted into the bones of the skull, the vertebrae, 

 the ribs, the sternum, the coracoids, the pelvis and the femora. 



In the Emeu and Cassowary, whose pectoral members are much reduced in size, use- 

 less for anything like flight, and serving, so far as is known, only for some feeble actions 

 of defence, the air is less freely admitted to the bones of the trunk, but still penetrates 

 the femur. 



In the Apteryx the rudimental wings are so minute, that the fact of their retention of 

 the typical structure requires careful dissection for its demonstration : and in this species 

 we find the lungs confined to the thoracic-abdominal cavity, and not extended into any 

 part of the skeleton. The Dinornis presents an intermediate condition between the 

 Apteryx and the Emeu in regard to the extension of the air-cells, which penetrated the 



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