Moreover, the gland is influenced by and influences the factors of body weight and growth with an extreme readiness and lability. Deficient general undernutrition leads to rapid decline in its weight. Back in 1858, the pioneer student of the thymus, Friedleben, declared that the size and condition of the thymus is an index to be the state of nutrition of the body. Underfeeding for four weeks will reduce it to one thirtieth the normal. It seems to act as a storage and reserve organ, affording some protection against the limitation of growth by lack of food material. In exhausting or wasting disease, the weight of the gland sinks much more quickly than other glands. Scattered instances have been reported of children growing, putting on inches in height and expanding mentally, when thymus was fed to them, in whom every other measure previously tried had failed. A French study of over four hundred idiotic children with normal thyroids reported that over three fourths had no thymus at all. Everything points to the most direct and close relation between the gland and nutrition and growth, but with nothing tangibly definite like our knowledge of the thyroid and the pituitary. There is evidence that the thymus is involved in the health and efficiency of muscle cells and muscularity. Certain tumors of the thymus, presumably destructive of the gland substance proper, and thus cutting off its secretion, are accompanied by a singular muscle weakness and atrophy of the muscle cells, entirely out of proportion to the general damage suffered by the other cells of the body when affected by the poison of a malignant growth. Also, the thymus has been discovered diseased in certain mysterious progressive muscular wastings. A remarkable fatigability of muscles, which appears after the slightest exertion, is a feature. The feeding of thymus has caused muscle cramps which apparently depends upon an increased excitability of the muscle nerve endings. Feeding of thymus to some of the lower creatures of the animal kingdom will completely hold up differentiation. Take the unfolding of the specialized tissues and organs which transform the tadpole into the frog and the chrysalis into the butterfly. A tadpole kept supplied with enough thymus in a nutrient medium will swell into an extraordinary giant tadpole, but will not change into a frog. Recently, this experiment has been contradicted. Yet this effect corresponds to the conception of its importance in childhood as a retardant of precocity, physical and mental. Clinical observations emphasize that in childhood it is the chief brake upon the other glands of internal secretion which would hasten development and differentiation, checking them perhaps for a given time and so profoundly influencing growth. THE PINEAL