The tiny collarbones (clavicles) lead the way as the embryo’s soft tissue skeleton begins to harden. Inside the body, the sex glands begin to differ in male and female embryos. 

This specimen is part of a collection of real human embryos and fetuses ranging from 28 days to 38 weeks, capturing the stages of growth and development before birth. The specimens were collected by Dr. Helen Button with help from Chicago hospitals Loyola Medical Center and Michael Reese Hospital during the difficult times of the Great Depression in the 1930s. To the best of our knowledge, all failed to survive because of accidents or natural causes. Dr. Button obtained the parents’ permission to use these specimens as teaching tools.