thirty children, varying in age from fifteen days to six months, was 140 when awake and 121 when asleep. In another group of twenty-nine children, between the ages of six months and twenty-one months, the average was 128 when awake and 112 when asleep. The observations of Hohl and Allix[8] indicate that among very young children the difference between the pulse of sleep and the pulse of wakefulness may equal forty beats. According to Guy (loc. cit.) the pulse is more variable in the morning than during the afternoon or evening.

Temperature.—Aside from the almost hourly fluctuations of the bodily temperature, a noticeable sinking of the temperature-curve is observed during the hours of sleep. This alone is sufficient to indicate a diminished rate of combustion in the tissues. Boussingault found[9] that a dove which consumed 255 millegrammes of carbon every hour while awake, oxidized only 162 millegrammes when asleep. Scharling also observed that the quantities of carbon successively oxidized by the same man when asleep and awake bore to each other the ratio of 1:1.237. The observations of Demme[10] indicate that increase of bodily temperature during the hours of sleep must be considered as the result of pathological processes in the tissues. The observations of Allix (loc. cit.), made upon sixteen children during the first twelve days after birth, showed an average fall of 0°.38 C. during the hours of sleep. Eight children, between five and sixteen months old, exhibited a similar depression of 0°.56 C.; while ten children, ranging in age from twenty months to four years of age, averaged 0°.34 C. less when asleep than when awake.

The well-known experiments of Chossat, who found that the temperature of pigeons was from 0°.70 C. to 0°.90 C. higher at noon than at midnight, may not be considered satisfactory evidence of the depressing influence of sleep, because it is true that the diurnal variations of temperature which are conditioned by the vital activities of every animal might be sufficient to account for these differences. The experiments of Horvath[11] are more convincing. This observer found that the marmots upon which he experimented were accustomed to sleep during the winter for about four days continuously, and would then remain awake for an equal length of time. “During the sleeping period they can be cooled down to such a degree that a thermometer introduced into the rectum to the depth of an inch and a half indicated only 3°F. above the freezing point. The temperature rose rapidly after the animal awoke, so that in the course of an hour it was 3°F. higher; at the close of the second hour 9°F. higher, and at the end of the next half hour about 27°F. * * Neither respiration nor the muscular movements were correspondingly augmented.” This observation clearly shows the powerful influence of cerebral activity upon the liberation of heat within the body.

Secretion.—The functions of the numerous glands throughout the body are diminished during sleep. The tears dry up, and the cornea receives less moisture. Hence the stickiness of the margins of the eyelids during the sleep of a patient suffering with conjunctivitis. He can open his eyes, on awaking, only after sufficient time has elapsed to revive the lachrymal flow. Exner[12] remarks the diminution of pathological secretion in nasal catarrh during the hours of sleep. The mouth in like manner ceases to receive its full quota of saliva, and its cavity quickly dries if the lips remain open. The secretions of the gastro-intestinal glands vary with the contents of the alimentary canal; but in general they are considerably diminished, and digestion is correspondingly retarded during the hours of sleep. The quantity of urine is lessened during sleep.[13] The elimination of urea and of other excrementitious matters is less during the night than by day.[14] Unless increased by disease, or by accidental circumstances connected with atmospheric temperature and unnecessary clothing, the perspiration is also diminished.

Nutrition.—All the molecular processes of nutrition are reduced by sleep. The lowering of the bodily temperature has been already indicated. The observations of Helmholtz[15] indicate that the actual liberation of heat in the tissues is but little more than one-third of the amount set free in an equal period of time during the waking hours. The numerous experiments[16] of Boussingault, Henneberg, Scharling, E. Smith, Liebermeister, Pettenkofer, Voit, and Lewin, clearly indicate the fact that during sleep less oxygen is absorbed, and less carbonic acid gas is discharged, by the tissues. Voit found that while, during the daytime, 435 grammes of oxygen were taken in by a working man, only 326 grammes were needed by the same individual during the nocturnal half of the day. Artificial sleep occasioned by chloral hydrate produced a similar reduction in the consumption of oxygen and in the formation of carbonic acid gas. Under the influence of morphine the reduction of CO_2. reached 27 per cent., and the diminution of oxygen amounted to 34 per cent. of the quantities furnished during wakeful activity. The comparatively small reduction (only 6 per cent.) in the decomposition of the nitrogenous elements of the body during the same period, exhibits the close relation between the metamorphosis of the non-nitrogenous elements of the tissues and the amount of bodily activity.

The experiments of Pettenkofer and Voit, to which allusion has just been made, serve also to illustrate the fact that all tissue changes are increased by every excitement of the sensory organs of the body, but are diminished by the subsidence of peripheral irritations. Hence the importance of quiet and darkness when we seek to induce that state of the body in which molecular processes should reach their minimum. Since every act of perception is attended by an outburst of refuse matter from the nervous tissue, the quantity of such excrementitious discharge in any given period of time becomes in some sort a measure of the vital activity of the organism. Conclusive proof of the diminution of vital function during sleep is thus obtained.

It must not, however, be inferred that the general reduction of tissue-change, which has thus been established, during the hours