2S-J: Studies of the Develoi)ment of the Human fSkeJcton 



ences of this nature, though by no means marked, are none the less to be 

 made out. His conclusions have been confirmed by Veit, 89, Eomiti, 92, 

 Konikow, 94, Thomson, 99, and Merkel, 02. Petersen has made most 

 careful comparisons between the measurements of the pelvis he recon- 

 structed and the structural data furnished by Fehling; The variations 

 due to sex are, however, so slight that they are likely to be obscured in 

 wax reconstructions of early embryos. Allowance must be made for 

 errors of technique and for the difficulty of determining corresponding 

 points between which measurements are to be taken. Thus, for instance, 

 the proportional widths of the entrance to the true pelvis, the pelvic 

 cavity and the pelvic exit I find to be in CXLV as 100 : 75 : 54, while 

 Petersen makes them for Lo^ as 100:74.7:46.1. According to theory 

 the width of the exit should be proportionately less in the male than in 

 the female pelvis. For foetuses of 30 to 34 cm. Fehling gives for females 

 100 : 88 : 70 ; for males 100 : 87 : 60 ; for new-born females 100 : 84 : 76 ; 

 for new-born males 100 : 82 : 65 ; for adults 100 : 92 : 81. Without the 

 possibility of a direct comparison of the two reconstructed pelves it is 

 therefore scarcely possible to determine accurately to what extent they 

 may show sexual differences. A characteristic on which Merkel, 03, 

 lays especial stress, the more posterior position of the greatest width at 

 the pelvic entrance in the male, does, 1 think, exist in CXLA^ in com- 

 parison with Lo^. 



These two embryos show that at the beginning of the third month of 

 development the cartilagenous pelvis is well formed. At this time, also 

 ossification begins in the ilium. Preliminary changes in the cartilage 

 may be seen in embryos of 25 mm. in an area corresponding to that in 

 which chondrofication commenced. These changes are further advanced 

 in CXLV, but in this embryo neither deposit of calcium salts nor true 

 ossification has commenced in the ilium although ossification is under 

 way in the clavicle, inferior and superior maxillae, occipital, humerus, 

 radius, ulna, femur, tibia and fibula. Another embryo of the same 

 length, 33 mm., LXXIX, does, however, show a well-marked area of 

 ossification, Fig. 58. In the endochondral region calcium salts are de- 

 posited while on each side of this perichondral ossification takes place. 

 In an older embryo, LXXXIV, length 50 mm., this latter process shows 

 well, Fig. 36. It is known that ossification of the ischium and pubis 

 takes place considerably later, that of the ischium beginning in the 4th 

 month and that of the pubis in the 6th to 7th (Bade, 00). 



Aside from the ossification of the ilium nothing especially notewortliy 

 seems to take place in the development of the pelvis during the period 



