PRESENT PROBLEMS IX EVOLUTION AND HEREDITY. 319 



shifting- of the pelvis upwaicL wlieiel).\ a lumbar vertebra is acbled to 

 the sacrum and subtracted iVoni the dorso-luinbar series. 



Cuimiughani has found that the division of the neural s[)iiies in the 

 upper cervical vertebra' distinj;uislies the ]ii.i>her races from the h)wer.* 

 The si)ine of tiie axis is always biHd, but the spines of the cervicals 

 three, four, and live, are also, as a iiile, bitid in the European, Mhile 

 they are single in tlie lower races. The same author shows that the 

 bodies of the lumbar vertebi;e are altering, by wjdeninj;' and shorten- 

 ing, to form a tii'inei- ])illar of support, with a com|)(Misating increase in 

 the length of tiie inteiverteltral cartilages.t In the child, the vertebra*, 

 inesent more nearly their primitive elongate compressed form. With 

 this is associated an increase of the forward lumbar curvature (Tur- 

 ner);! the piimitive (/. r., Simian) curve was backward: even in the 

 negroes the collecti^"e measurement of the posterior faces of the live 

 lumbars is greater than the anterior, in the proportion of KM) to 100; 

 whereas in tlie white the collective anterior faces exceed tlu' ]»osterior 

 in nearly the same i)roportion — 100 to 9(5. 



The lower region of the back is also the seat of one of tlie most inter- 

 esting and imi)ortant of the ciumges in the body, namely, the correlated 

 evolution of the inferior ribs, the lumbar vertebra', and the pelvis, — to 

 which cnd)ryology, adult and com]»arative anaton\y, ami reversion all 

 contribute their ipiota (»f proof In most of the anthropoid aj»es, and 

 therefoi-e presumably in th<' pro-anthropos, theie were thirteen com- 

 plete ribs and four lumbar \-ertel)ra', while man has tweh'c ribs and 

 live lumbais. Thus we luay consider the superior lund)ar of adult 

 man as a ribless dorsal: not so in the hunuin embryo, however, for 

 Rosenberg^ has found a cartilaginous I'udiment of the inissing thir- 

 teenth ril) upon the so-caHed first ]und)ar. Atavism contributes an 

 earlier chapter in tlie histor\' of this ivgion, for llirmingham || reports, 

 out of fifty cases examined in one year, two in which there were six 

 lumbars, and in each the thirteenth rib was well developed: this is an 

 interesting example of "correlated revei'sion," for as the jtchis shifted 

 downward to its ancestral })ositi(/ii u])on the twenty-sixth vertebra, 

 the thirteenth rib was also restored. The other ribs are in what the 

 ancients styled a "state of tlux;" our eighth rib has been so recently 

 floated from the sternum that, and according to ('uiiniiigliam,*] it re- 

 verts as a true rib in twenty cases out of a hundred, showing a decided 

 preference for the right si(h'. IJegarding also tlu' occasional fusion of 

 the iittli lumbar with the sacrum and the unstable condition of the 

 twelfth rib, which is by variation rudimentary or absent, Koseiiberg 

 makes bold to i)redict that in the man of the future the ])elvis will shift 

 another step U])ward to the twenty fourth Aertebra'. and we shall tlK'ii 



■ Joiiriuil of Anatomi/ and J'tiiiniolofin, ^ Morph. Jahrh., ISTl!. 



1886, p. 63(5. ||./o»r//«/ of Anafovui (iiid ]'lii/si<ilo<iy, 



i Ibid., 1890. p. 117. 18!»1. p. 526. 



tibid, 1887, p. 473. H Ibid., 1890, j). 127. 



