Recent experimental work in the physiology of the thymus has cleared up matters in two directions, namely, the relation of the organ to growth and to the condition of the bones, on the one hand, and to the electrical excitability of the nervous system, on the other.
When one completely extirpates the thymus of a young dog in the first weeks of life, there occurs as a consequence not only a checking of growth, but a condition in which the bones become softer and more flexible and show a smaller callus after an artificially produced fracture, than is seen in a control animal of the same brood. If one tests the electric stimulation of a young dog over the median nerve or the cerebrum, before and after the extirpation of the thymus, one can demonstrate after extirpation a gradually increasing hyperexcitability, which may be raised to the same degree as