how it arrived at the mathematical precision of its cell. This can only be understood by a knowledge of facts and laws gained through centuries of work, and then perhaps they would not suffice for a truc solution of the mechanism of the beehive. Man had for ages looked with awo on the lightning, but no amount of contemplation could have re- vealed its meaning; it could only be understood when the laws of electricity were applied to explain. its phenomena, and these were learned step by step supported on so simple a basis as the effects of rubbing a piece of wax. The glories of the bow in the skies though gazed at for ages had never suggested the interpretation of the spectrum, but it was by the observation of a ray of light passing through a hole in a window of a small room that the meaning of the rainbow was revealed.
So in physiology we are apt to forget that it is by slow work, step by step, and often quite apart from the subject whose interpretation we seek, that we obtain fruitful knowledge. No contem- plation of the human eye would have suggested the camera, but the building up of the camera by a series of inventions explained the mechanism of endeavoured to teach the the cyc. We have
