Karl B. is the son of sturdy parents, both of whom were born and reared in the Swiss Tyrol. He had never developed like the other children—was, in fact, much smaller at five and a half years than the fourteen-months-old baby. He was dull, placid, taking no note of his surroundings, sitting or lying just where he was left, and never evinced any disposition to play or converse with the other children. I saw this child on the 4th day of January, 1908, in a purely accidental manner. The parents had been told by their attendant that the child had either rickets or was an idiot, and they in consequence had kept the child in the background for two or three years, being very much chagrined and mortified at the prospect of bearing through life the burden of hopeless idiocy. The child had such classical symptoms of cretinism that I asked permission of the family to treat him for awhile, though it required some persuasion, because of the fact that they felt it was time and money wasted. On the 5th day of January, 1908, the child was five years and a half old, twenty-eight inches in height, circumference of chest twenty-one, abdomen twenty-three. He was given one and one-half grains of thyroid extract twice daily, the dose being gradually increased until he showed signs of irritability, with accelerated pulse. The child's extremities soon warmed up, the circulation became better, the hair began to grow, the child for the first time in its life walked and talked, began to take note of surroundings and to play with the other children. Just one year after the beginning of the treatment—January 5, 1909—the child was thirty-five and three-quarter inches in height, chest twenty-three, abdomen twenty-three. This disease, sometimes known as cretinoid or myxoedematous idiocy, was first described by Fagg in 1871. Since then a number of cases have been published, both in England, on the Continent and in America, showing that the disease is not confined to any one country. While the disease is comparatively rare, cretins are more common than was formerly supposed. The disease seems to be in reality a pachydermatous cachexia, and it is now, I believe, well established that it is caused by congenital absence of the thyroid gland or to the presence of something which abolishes its functions. Little is known as to the causes of its destruction or abolishment of function. As a rule only one case occurs in a family, the other members presenting nothing abnormal in their mental or physical development, hence the term sporadic. It has been more frequently reported in the Tyrol, in Switzerland, a coincidence which makes this child's case all the more interesting, in that both its parents are physically and mentally well up to par and the other children possess even more than the average intelligence.