266 



As this is a specimen from a case wliich was obtained in the recent 

 state there was no difficulty in ascertaining these facts. 



As a rule the deficiency in bony tissue in a rudimentary rib, or 

 the loss of its individuality through its fusion with the neighbouring 

 rib, occurs in its distal portion. This anomaly may occur however 



at any part of the 

 costal arch and 

 throughout a greater 

 or less extent of its 

 length. 



Fig. X shows a 

 case where fusion of 

 the first dorsal rib 

 has occurred in the 

 middle of its extent 

 or rather at the site 

 of crossing of the 

 artery. A similar con- 

 dition occurs in the 

 present series but the 

 fusion of the two ribs 

 exists only in the 

 region of the crossing 

 of the vein (Case G). 

 (This latter condition 

 is not thought worthy 

 of a special figure.) 

 A further stage 

 in which the length 

 of the rib has been 

 affected most by the 

 artery is shown in 

 Fig. XL In this case 

 a well marked groove 

 is present on the ru- 

 dimentary rib for the 

 reception of the nerve 

 trunk, while the second dorsal rib exhibits markings for both artery 

 and vein. 



Fig. IX. 



Fiff. X. 



Fig. IX. Rudimentary first dorsal rib articulating 

 by means of an intervening cartilage with the second rib 

 (cf. Fig. 4). Case C. English. Adult. Male, 'h Nat. size. 

 To show fusion of a rudimentary first dorsal rib to 

 the second dorsal rib. The chief factor in the production 

 of this specimen would appear to be the artery. None 

 of the rib is present in front of the vessel in consequence 

 of the situation of the vein which makes an impression 

 even on the second rib. Figures IX, X, XI, illustrate 

 similar condition arrested at different stages. 



Fig. X. Partial fusion of first and second dorsal 

 ribs. Case 2/1250. Nubian series. Female. Age 18 — 20. 

 V» Nat. size. 



The nerve groove is only slightly marked on this 

 specimen and occurs on the inner border only. It cannot 

 he shown in the figure but its situation is indicated at N. 

 The ai'terial and venous impressions are well marked at 

 the inner border; while the rib in this specimen has been 

 subject to the influence of nei've artery and vein its 

 general appearance indicates that the influence of the 

 artery has been the dominant factor in its fusion with 

 the neighbouring bone. 



