Bone as a mineral reserve.

2. Part of epiphyseal cartilage of upper vertebra shown in I. Long columns of cartilage cells, indicating the intense activity of the cartilage, are evident. x 130. 3. Part of epiphyseal cartilage of lower vertebra shown in I. Cartilage columns are shorter than those in 2, indicating less marked activity of the growth cartilage. x 130. 4. Sagittal section of lumbar vertebrae of mature rabbit showing persistence of epiphyseal cartilage in upper vertebra. This figure demonstrates that the more active epiphyseal cartilage in a bone tends to persist longer. The lower end of a vertebral body in most pronogrades is the ‘growing’ end. x 10. 5 . Section of upper end of femur of newborn child. The ends of most long bones before ossification are nourished by vessels running in cartilage canals. Some of the vessels pass from the diaphysis into the cartilaginous end and an example of this is seen in this figure. The cartilage is in the upper part of the figure and the diaphysis of the bone towards the lower part. x 86.