YOUR correspondents on this subject in the last number of NATURE entirely agree with me that “a medical man should have some knowledge of natural philosophy and its applications to the conditions with which he Has to deal;” but there are one or two points on which they seem to have misunderstood me. As one of the examiners who set the question challenged by Mr. Heath, I defended it, and pointed out that it bore a very close relation to medical science, besides showing, by the simplicity of the solution, that it was one of the mildest questions which could be set.