264 



definite statement as the condition was only discovered after macera- 

 tion. But in this type of case the rib has escaped interference by 

 nerve and artery but has been affected by the vein. 



That the vein has considerable influence on the appearance of 

 the upper aspect of the rib is obvious from the great variety of im- 

 pression made by it on otherwise normal specimens of first rib 

 (see Fig. VIII.) 



The most extreme type of a seventh cervical rib is illustrated in 

 Eig. VI. 



In this case the rib is complete and articulated with the sternum 

 by means of a costal cartilage. It presents markings for the nerve 



and for both artery and vein, but 

 of these markings that for the artery- 

 is less defined than that for either 

 of the otiier two structures — a con- 

 dition to be expected from the 

 normal relations of the thoracic 

 operculum. 



In the above types reference 

 lias been made to every stage in 

 the production of cervical rib from 

 its most rudimentary appearance 

 to its complete form. Many of 

 the specimens Avere obtained in 

 the recent condition and therefore 

 the relation to surrounding struc- 

 tures, more especially to the 

 nerves and vessels, could be 

 studied and thus correct inter- 

 pretation given to the varieties of 

 impressions found upon the bone. 

 We have now to consider 

 those conditions in which not 

 only is there no inclusion of ad- 

 ditional skeletal tissue in the thoracic operculum, but where the inlet 

 presents a diminished costal arch. These are known as instances of 

 rudimentary first rib. 



Fig. VI. Seventh cervical vertebra 

 and rib. Case89/731. Nubian series. Adult. 

 Male. '/2 Nat. size. 



This drawing shows a complete cer- 

 vical rib marked by impressions for nerve, 

 artery and vein. It articulated with the 

 sternum by means of the costal cartilage. C.C. 



