ix PSYCHO-PHYSICAL PHENOMENA 463 



Much sleep, in fact, induces plumpness, while wakHulurss tends to 

 emaciation. 



Volkow (1900) described the sleep of inanition in the liojka, or 

 winter fast of the poor mujiks on the Eussian steppes, who lit- 

 silent in bed for the greater part of the cold season. This 

 is not, however, a physiological sleep, but a hibernation, similar to 

 that of marmots and hibernating animals in general. 



Secretions, generally speaking, diminish during sleep. The 

 lachrymal secretion begins to decrease, as we have said, when 

 drowsiness sets in. The salivary and mucous secretions also 

 diminish, as proved by the common fact that the mouth and 

 nostrils become dry in sleep. 



The secretion of urine diminishes in sleep, and has con- 

 sequently a higher specific gravity in the morning than during the 

 day. Urine secreted by night produces convulsions, that secreted 

 by day has a narcotic effect when injected into animals (Bouchard). 



Cutaneous perspiration, on the other hand, increases during 

 sleep. Santorio affirms that a man perspires as freely in seven 

 hours of sleep as in fourteen when awake. 



The respiratory rate is slower during sleep, and may become 

 intermittent or even periodic, especially in children and old people 

 (Mosso, Luciani) ; the inspiratory movements of the diaphragm 

 almost disappear, so that the abdominal type becomes costal 

 during sleep. Each inspiration is longer, and the expiration 

 shorter. 



The output of carbonic acid is considerably diminished during 

 sleep (Pettenkofer and Voit), owing particularly to the inactivity 

 of the muscles ; while the oxygen absorbed is partially stored up 

 in the blood and tissues. 



The beats of the heart slow down during sleep ; pulsus in somno 

 parvi, languidi, rari, wrote Galen. But the action of the heart is 

 not uniform throughout the whole period of sleep ; it increases as 

 the moment of waking draws near (Double"). A fall in arterial 

 pressure has also been noted during the first five hours of sleep, 

 followed by a rise up to the moment of waking (Frangois-Franck, 

 1881 ; Brusch and Fayerweather, 1901). In general, the tone of 

 the involuntary muscles of the intestines, bladder, etc., is depressed 

 during sleep (Mosso, Pelacani, and others). 



The peripheral vessels are congested during sleep owing to the 

 slowing of the circulation and the diminished tone of their walls 

 (Mosso, Franqois-Franck). This effect increases up to the second 

 hour of sleep, and then decreases to the moment of awakening 

 (Howell, Lehmann). 



The study of sphygmograph and plethysmograph tracings 

 taken during sleep shows periods of automatic constriction and 

 dilatation of the blood-vessels. Sensory stimulation during sleep 

 produces quite different vasomotor effects from those that result 



