269 



(13) The costal anomalies at the upper end of the thorax are not 

 due to any one cause. They are errors in segmentation or 

 differences in the development of bony tissue which are asso- 

 ciated -with the presence of variations in the disposition of the 

 nerves and vessels in this situation. 



(14) In the present series instances of rudimentary rib of either 

 the seventh cervical or the first dorsal type have been met 

 with during infancy, about puberty and in adult age. 



Evidence shortly after birth shows that they may be 

 completely formed by that time. The frequency with which 

 the condition occurs and the singular lack of marking observed 

 clinically on so many of these cases which have been cured 

 by removal of the offending piece of bone, tend to cast doubt 

 on the usual teaching that these abnormalities are the cause 

 in every case of the symptoms sometimes associated with and 

 held to be occasioned by the presence of rudimentary ribs in 

 this situation. Full consideration of this last section does not 

 lie within the scope of the present investigation. 



Appendix I. 

 Analysis of Types Illustrated in the Present Inyestigatiou. 



I. Types in the Ascending Scale. 

 i. e. Rudimentary seventh Cervical E.ibs. 



(1) Cut short by nerve: 2 specimens, both on right side: One adult: One 

 infant 12 months old. (Fig. III.) 



(2) Cut short by artery : 3 specimens : in each case the rib was not cut off 

 but fused directly or by means of an intermediary cartilage with the 

 first dorsal rib. Occurs twice on left side; once on right. All adult 

 specimens. (Fig. IV.) 



(3) Cut short by vein : 4 examples — two right : two left. All adult. (Fig. V.) 



(4) Complete cervical rib articulating with sternum. One example : Adult — 

 right side. (Fig, VI,) 



II. Types in the Descending Scale. 

 i. e. Rudimentary first Thoracic Ribs. 



(5) Fusion with second rib at anterior extremity only (crossing of vein) 

 one case (G-) right side. 



(6) Greater or less amount of fusion of first and second dorsal ribs extending 

 from crossing of artery forward. Two examples: both adult: both 

 right side. (Fig, IX.) 



(7) Fusion of first and second ribs at site of crossing of artery. One 

 example: left side: age 18—20. (Fig. X,) 



(8) Cut short by artery: One example: left side: adult. (Fig. XI,) 



