There are certain other singular by-effects of the gland in its relation to the periodic phenomena of the organism like hibernation, sleep, and the critical sex epochs of both sexes. In hibernation, or winter sleep, the animal in cold weather passes into a cataleptic state in which it continues to breathe, more deeply but more slowly than when awake, but shows no other signs of consciousness or life. A lowered blood pressure and a marked insensitivity to painful and emotional stimuli go with it. There is a preliminary storage of starch in the liver, and of fat throughout the fat depots of the body. These are so like what happens after part of the pituitary is removed, that a comparison of the two becomes inevitable. Common to both conditions is a drop in the rate of tissue combustion or metabolism, which can be relieved by injection of an extract of the pituitary, a rise of temperature occuring simultaneously. Moreover, examination of the glands of internal secretion of hibernating species, like the woodchuck, during the period of hibernation, shows changes in all of them, but most marked in the pituitary, the shrunken cells staining as if they too were asleep, or in a resting stage. The characteristic alive qualities of these cells return, without relation to food or climate, when the animal comes to in the spring, at the vernal equinox. Hibernation may, perhaps, be put down to a seasonal wave of inactivity of the pituitary gland. Now winter sleep may be looked upon as an exaggeration of ordinary night sleep, the latter differing from the former only in its brevity. In the natural sleep of non-hibernating species there occurs, too, a fall in temperature. Moreover, they all, even man, have a certain capacity for winter sleep, as the experiences of travellers and explorers in the arctic regions indicate. In certain parts of Russia, where there is a scarcity of food during the winter months, the peasants pass weeks at a time in a somnolent state, arousing once a day for a scant meal. Just as the sex glands influence the body and mind profoundly with a certain cyclic periodicity of activity and inactivity (rut, heat, menstrual period and so on), which has been demonstrated to have a very close functional relationship with the pituitary, so sleep and hibernation will bear interpretation as products of a temporary dormancy of the same gland. We have, then, to set up in the place of Morpheus and Apollo, the new gods of the internal secretion of a chemical-making bit of the brain, as an explanation of the rhythms of sleep and wakefulness.