A. B. Bruce addressed the doctrine of Christ's humanity in a series of lectures that later became The Humiliation of Christ. This work presents a review of historical theories regarding Christ's humiliation, from the church fathers through Bruce's own time, along with a defense of what he believed to be orthodox views on the subject. A. T. Robertson called it "Bruce's Masterpiece."
The idea that Christ "emptied himself" (as Paul writes in Philippians 2) has always been difficult to grasp and may even be called one of the great mysteries of the faith.
If you own one of the Logos Bible Software base products, you're probably familiar with Bruce's Training of the Twelve. The author's theological and pastoral sensitivity make him a joy to read, and he still has many valuable insights to offer today's reader. You will see Bruce's Humiliation of Christ cited in the bibliography of Bible dictionary articles on "Incarnation" or "kenosis."