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A Note on Some modifications inthe morphological 

 Structure of the Mammalian Vertebr/e. 



By A. ZiETz, F.L.S., C.M.Z.S. 



[Read September 4, 1906.] 



The morj^liological changes which the vertebrae present 

 when we comj^are certain modifications in the apophyses, right 

 through the whole of tlie mammalian series, appear almost 

 as a blank, even in more recent publications. I selected for 

 comparison of these transformations the vertebrae of the lum- 

 bar series, for the reason of their simplicity in structure, in 

 preference to the dorsal series, which are subject to many com- 

 plications. 



In human anatomy the lumbars show the usual forms 

 of apophyses, with the exception of one of these, which is 

 only indicated and known as the tubercle; this is the ana- 

 pophysis. 



A step further downwards in the mammalian order shows 

 that the tubercle becomes more or less pronounced, till we 

 arrive at the marsupialia, where in some instances they ap- 

 pear as a rather conspicuous element. So far, these changes 

 do not seem to affect the diapophyses, except in one instance, 

 recorded by Professor Owen. This is in Os'phranter rufus* 

 in which they are marked by the reduction to a small rudi- 

 ment, but only in the first lumbar. As we step still further 

 back to the apparently ancient type, the Diprotodon of Owen, 

 the lumbars at a first glance strikingly resemble the lumbars 

 of man, except in one point ; this is the entire absence of 

 the tubercle. A more detailed investigation, however, re- 

 veals the fact that what at a first glance appeared to be the 

 diapophyses are in reality the anapophyses, which in this 

 case are transformed into the long, flat, lateral expansions 

 which in other mammalia characterize the diapophyses, but 

 the latter are either absent or occur as a rudiment con- 

 nected with the anapophyses, which would be just the re- 

 verse to what happened in the lumbars of man. 



* Professor Owen : On the Osteology of the Marsupialia. Trans. 

 Zool. Soc. L., vol. ix., part viii., page 429, pi. Ixxv., fig. 11. 



