(Cervical RiIas in Men. 83 



Neck ril) sup))rcssion is further evidenced by the absence of costal 

 processes from the seventh cervical vertebra of the (|uadriipedal mam- 

 mals. Tlie absence of these costal processes shows that the rib- 

 structure which is associated with the seventh neck bone may, under 

 the influence of the neck Mexion that occurs in the quadrupedal 

 mammals, suffer extinction. 



The development of cervical rilis in the mammalian neck may be 

 either partial or complete. 



(a) T'artial in the short cervical ribs tiiat do not reach tlie 



sternum, as seen in duf>'onp;s and man. 



(b) Complete in the sternal cervical ribs of the manatee and in 



the occasional sternal cervical ril)S of man. 



Function of Ribs. 



Ribs are stiff and resilient. The uses to which these (jualities are 

 put by the animal economy constitute the functions of ribs. 



Fish-ribs stiffen the l)ody and protect viscera, but they possess no 

 respiratory function. 



In the chameleons, the sphenodon, and other lizards possessing a 

 low grade of neck development, cervical ribs are continuous with the 

 ribs of the body-cavit}', their function being to protect viscera and to 

 assist respiration. In snakes the cervical ribs are greatly developed 

 and their function is locomotory. The cervical rib-stumps of the 

 crocodile afford muscular attachments, and they confer some degree 

 of rigidity upon the neck. 



The costal processes of mammals are too small to interfere with the 

 freedom of the movement of the neck, and they serve merely for 

 muscular attachments. The nuiin function of the thoracic ribs is 

 associated with respiration, and the rib development that occasionally 

 taKes place in the mammalian neck is also intimately associated with 

 the lungs. Therefore 



Cervical Ribs of Mammals are of Respiratory Function. 



Cervical ribs have been variously described: — Keen, in 1907, re- 

 ferred to them as "" congenital anomalies " ; Andrews, in Keen's Sur- 

 gery, calls tliem "' deformities." Purves Stewart records that Oppen- 

 heim regards cervical ribs in the human neck as the '' stigmata of 

 degeneration." Here and there cervical ribs are regarded as examples 

 of atavism, but the majority of medical men regard them as vestiges. 



The term " congenital anomaly " can only be used in a very re- 

 stricted sense because science cannot regard any natural condition 

 as anomalous. The word ' deformity "' conveys no idea as to what 

 causes the development of cervical ribs. The expression '' stigmata of 



