Charles R. Bardeen 285 



when the embryo is growing from 30 to 50 mm. in length. Fig. 13 shows 

 the form of the pelvis in an embryo of the latter size. 



The relations of the pelvis to the sacrum dnring the second and third 

 months of life deserve some attention. I have endeavored to illustrate 

 them in Fig. 44. The curves of the spinal columns of several embryos 

 and an adult arc there shown. A point " a " represents the place where 

 a line joining the centers of the two acetabula would cut the median 

 plane of the embryo. From this point dotted lines are drawn to each 

 extremity of the sacral region and one is projected perpendicularly to a 

 line joining these two extremities. A fourth line from point " a " indi- 

 cates the direction of the long axis of the femur. 



In Embryo II, length 7 mm., the leg skeleton is not differentiated. 

 " a " represents there the approximate position where the pelvic blastema 

 will first become marked, as in Embryo CLXIII, length 9 mm. The 

 perpendicular falls on the body of the 1st sacral vertebra and points 

 toward the mid-thoracic region. 



In Embryo CIX, length 11 mm., the perpendicular falls on the 1st 

 sacral vertebra; in CXLIY, length IJ/. mm., about at the junction of the 

 2d and 3d; in CVIII, length 22 mm., on the 3d; in CXLV, length 

 S3 mm., at the junction of the 2d and 3d; in CLXXXIV, length 50 mm., 

 on the anterior portion of the 3d. 



At birth, judging from the figure of Fehling, the perpendicular would 

 strike at about the junction of the 2d and 3d. In the adult the area 

 where it strikes shows much individual variation, but in most of the 

 specimens which I have examined it strikes on the 2d sacral vertebra 

 not far from the junction of this with the 3d. In some specimens it 

 strikes the 3d. The material at my disposal has been chiefly dried 

 specimens from the dissecting room and has been subjected to some 

 warping. 



Fig. 44 shows that when first differentiated the pelvis occupies a posi- 

 tion anterior to that which it takes when it becomes attached to the 

 vertebral column, but that after this attachment the position of the 

 central area of the acetabulum is altered but slightly with respect to the 

 sacral region of the vertebral column. At the beginning and at the end 

 of the period under consideration it probably occupies a position slightly 

 more anterior than that which it takes during the latter part of the 

 second and first part of the third month of development. The chief 

 alteration of the position of the pelvis with respect to the long axis of 

 the body is due to change in the position of the sacrum in relation to 

 the rest of the spinal column. 



Merkel, 02, has contributed an important paper on the growth of the 



