PHYSIOLOGY OF SLEEP—LEGENDRE. 593 
tion; still, the perspiration is then profuse, and Sanctorius states that 
one perspires as much during 7 hours of sleep as in 14 hours when 
awake. The kidneys are active at night and the urine in the morning 
is generally denser than in the daytime. According to M. Bouchard, 
who studied the effect of urinal poisons by injecting them into ani- 
mals, those formed during sleep are convulsive and those formed when 
awake are narcotic. By their mixture much of the poisonous effect 
is lost. 
Respiration is modified during sleep. It is easy to observe this in 
the case of those who snore, although the cause of snoring is little 
known. Generally the respiration is retarded during sleep, being 
deeper and more regular. In order to study this carefully, Mosso 
applied to his chest a pneumograph, which indicated the respiratory 
movements during sleep as well as when awake, and he established 
the fact that the inspirations are longer and the expirations shorter; 
the thoracic movements’ are greater than the abdominal ones; the 
rhythm is modified and from time to time the inspirations are replaced 
by distinct series, by pauses, or by more feeble respirations. Respira- 
tory changes have been studied thoroughly by Pettenkofer and Voit, 
who used for that purpose a chamber of 12 cubic meters capacity 
made of sheet iron, in which a man could remain for several days, 
as the ventilation was regulated by two suction pumps. The atmos- 
phere was analyzed as it came from the room and the amount of 
-earbon dioxide eliminated was found to be less durimg sleep. St. 
Martin, who made his experiments on a turtledove, reached the same 
conclusion. This diminution of the amount of carbon dioxide exhaled 
may be due simply to cerebral repose in the absence of any muscular 
action, or to other causes. M. Raphaél Dubois has held the theory 
that the decreased exhalation of carbon dioxide is in proportion to 
an accumulation of the gas in the blood, which acts as an anesthetic 
up to a certain point, and then excites the centers of wakefulness. 
The body temperature generally decreases during sleep. Marie de 
Manacéine has observed that it falls as low as 36.45° C. during the 
summer and to 36.05° C. during winter, the lowest temperature 
occurring between midnight and 3 o’clock in the morning. The 
temperature of the brain also diminishes equally, according to observa- 
tions by Mosso, which will have our attention presently. 
The heart action is retarded during sleep. Former investigators 
discovered this by observing the pulse, and more recently this has 
been confirmed by definite experiments. Mosso, by the use of 
suitable instruments, was able to register the pulse in the forearm, 
the leg, and the brain. Fran¢gois Franck observed that the contrac- 
tions become weaker and the interval between heart beat and pulse 
beat is greater than when awake; the arterial pressure diminishes, 
38734°—sm 1911——88 
