Charles R. Bardeen 301 



Fig. 44. Diagram to show the curvature of the spinal column, the pro- 

 portional lengths of the various regions, the relation of the acetabula to the 

 sacral region and the direction of the long axis of the femur in a series of 

 embryos 7 to 50 mm. in length, and in an adult. Each curved line repre- 

 sents the chorda dorsalis of an individual. The cervical, lumbar and coccy- 

 geal regions of this are represented by the heavy, the thoracic and sacral by 

 the light portions of the line. The approximate position where a line join- 

 ing the centers of the two acetabula would cut the median plane is repre- 

 sented at "a." For Embryo II, In which the skeleton of the leg is not yet 

 differentiated the position of the future acetabula is deduced from Embryo 

 CLXIII, length 9 mm. (See Fig. 2.) 



The line passing in each instance from "a" and terminating in an arrow 

 point represents the long axis of the femur. For Embryo II, this line is 

 pointed toward the centre of the tip of the limb-bud. From " a " in each 

 instance a perpendicular is dropped to a line connecting the two extremities 

 of the sacral region. The numbers refer to the following embryos: 



2, II Length 7 mm. 



109, CIX " 11 " 



144, CXLIV " 14 " 



108, CVIII " 20 " 



145, CXLV " 33 " 



184, CLXXXIV " 50 " 



Ad. Adult. 



Plate XI. 



Fig. 45. Longitudinal section through the center of the limb-bud of 

 Embryo CLXIII. i// diam. Compare with Fig. 2. 



Figs. 46-52. A series of cross-sections through the right leg of Embryo 

 CIX, length 11 vim. 



Fig. 53. Outline of the blastemal skeleton with the regions marked 

 through which the sections 46-52 pass. 1^ diam. Compare with Figs. 3 

 and 4. 



Plate XII. 



Fig. 54. Section from Embryo CXLIV, length 14 mm., showing the 

 pubic, iliac and ischial cartilages. 14 diam. 



Fig. 55. Section passing longitudinally through the femur and tibia of 

 Embryo CLXXV, length 13 mm. A portion of the foot-plate is shown cut 

 obliquely. 14 diam. 



Fig. 56. Longitudinal section through the ilium, femur, and tibia of 

 Embryo XXII, length 20 mm. 14 diam. 



Fig. 57. Section through the pubis, ilium, ischium and head of the femur of 

 Embryo CCXXVII, length 30 mm. The hip-joint cavity shows well. It does 

 not extend into the region of the ligamentum teres. 14 diam. 



Fig. 58. Section through the ilium, ischium and head of the femur of 

 Embryo LXXIX, length 33 mm. Calcification is beginning in the ilium. 



Plate XIII. 



Fig. 59. Section through the leg and foot of Embryo XVII, length IS mm. 

 The section does not pass through the cartilage of the 1st metatarsal. 



