The consideration of the details of development and structure from a new point of view, I regret to say, is too incomplete and my opportunities have been too few to allow of the experimental work being completed in time for this meeting. I can only bring to your notice a number of what seem to me to be important questions bearing upon this subject for your discussion. When we consider the literature† at our command, we feel inclined to ask, "Is this reliable?" "Can we prove these statements?" And when we commence our line of proof by experiments, we meet with many obstacles. First, we find our education as regards our microscopic work has been neglected in college, or only given us from one side—the medical—with no dental bearing at all. What student is taught the principles of optics, illumination and the use of the condenser, which are so important