42 THE HUMAN STERNUM 



from scapula to sternum, is rudimentary in man, being overlaid and 

 replaced by the clavicle. Its extremities, however, are possibly persistent 

 in the form of the sterno-clavicular meniscus, and the cartilaginous inner 

 end of the clavicle on the one hand, and in the acromio-clavicular meniscus 

 when present on the other hand. 



The other elements present in the neighbourhood of the presternum 

 are the interclavicular ligament and the supra-sternal ossicles, the former 

 developing in membrane, representing probably the interclavicle, and the 

 latter, developing in cartilage representing the occasional recurrence of the 

 omosternum (PI. VIII, Fig. ^^). 



It is not impossible, however, that the suprasternal ossicles may 

 represent persistent and detached portions of the prae-coracoids,'' which are 

 responsible for the production of the menisci and inner portions of the 

 clavicles. 



In June of last year, in the Anatomische Gesellschaft at Heidelberg, 

 Dr. H. Eggeling" read a paper on the subject of the suprasternal ossicles, 

 fully confirming the foregoing observations. The chief differences in the two 

 series of observations lie in the fewer number of cases and the higher 

 proportions of ossicles or tubercles in Dr. Eggeling's experience. 



(^) Sterna/ Foramina cannot be said to be uncommon. One hundred 

 and thirty cases (20*2 per cent.) have been found among six hundred and 

 thirty-one sterna. The proportion among foetal sterna was 30"5 per cent. 

 They are always median and usually single. Occasionally two foramina occur 

 in the metasternum ; and in three instances foramina are found coincidently 

 in both mesosternum and metasternum. They are much more frequent 

 (Table XIV) in the metasternum (i6-4 per cent.) than in the mesosternum 

 (3*8 per cent.) When in the mesosternum the foramen is always in the 

 lower half of the bone ; most commonly opposite the attachment of the fifth 

 costal cartilages : and more frequently above than below that position 

 (PL VIII, Fig. 56). 



It is noteworthy that nothing in the least approaching the condition 

 of sternal fissure has been met with in this series. The foramina are small 

 in all cases ; the largest admitting nothing larger than an ordinary pencil. 



The explanation one has to offer for the occurrence of sternal foramina 



