THE HUMAN STERNUM 45 



The first costal cartilage is occasionally asymmetrical by reason of 

 increased depth and more extensive junction than usual with the presternum. 

 This occurs much more frequently on the right than on the left side 

 (28:5) (Table XVIII). 



The sixth costal cartilage and its attachment to the sternum arc interest- 

 ing on account of occasional asymmetry, and also because of the light 

 thrown upon the possible existence of a fifth clement in the mesosternum. 

 It is normally attached to the third or fourth piece of the mesosternum 

 (72-6 per cent.), and it is never displaced to a higher point. It is displaced 

 downwards in 27*3 per cent, of cases ; and more frequently articulates 

 between the mesosternum and the metasternum than with the metasternum 

 only. Asymmetry in attachment occurs forty-seven times out of one 

 hundred and forty-eight cases (31 "7 per cent.) It is much oftener displaced 

 downwards on the left (thirty-nine cases = 82*9 per cent.) than on the right 

 side (nine cases = i7'o per cent.) 



The seventh costal cartilage has its normal attachment between the 

 mesosternum and metasternum in 68-i per cent, of cases (Table XIX). It 

 is not commonly raised to articulate with the mesosternum alone (9*3 per 

 cent.), and when this does occur it is more frequent on the right than on the 

 left side (8 : 3). It is attached to the metasternum only in i^"] per cent, 

 of cases ; and when asymmetry occurs, the left cartilage is more often dis- 

 placed downwards than the right (44 : 1 2). It may fail altogether to articulate 

 with the sternum on one or both sides {6-6 per cent.) ; and the left is more 

 frequently absent than the right (4 : 30). This corroborates the idea 

 derived from an examination of higher cartilages : that a shifting downwards 

 of the costal cartilages in relation to the sternum is more common on the 

 left side than on the right, and, similarly, that there Is a firmer and closer 

 attachment of the right costal cartilages than of the left. 



The eighth costal cartilage has an occasional attachment to the sternum, 

 on one or both sides ; and more often on the right than the left side. The 

 results of observations made upon young sterna are given In Table XXI. 



As the adult sterna In my collection were mostly dry, and In many 

 cases lacked costal cartilages, one was unable, from their examination, to 

 arrive at conclusions which would be reliable. I have, therefore, specially 



