File:A text-book of human physiology (1906) (14770548935).jpg

Identifier: textbookofhumanp00tige (find matches)
Title: A text-book of human physiology
Year: 1906 (1900s)
Authors: Tigerstedt, Robert, 1853-1923 Murlin, John R. (John Raymond), b. 1874, tr
Subjects: Physiology
Publisher: New York and London, D. Appleton and Co.
Contributing Library: Columbia University Libraries
Digitizing Sponsor: Open Knowledge Commons

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terminations the carbon dioxide elimi-nation reaches its minimum in the second hour of sleep, and this probablyconstitutes to a certain extent the expression of the deepest sleep in a sleepingperiod of perhaps six to eight hours. The following peculiarities have also been observed in sleep. The eyes withpupils contracted are turned inward and somewhat upward. The respiratorymovements are less frequent than in the w^aking condition, and even in the manare mainly of the costal type. The respirations are also sometimes periodicallysuspended. The heart action is retarded; the vascular tone decreases in thecutaneous vessels and probably also in the visceral vessels, and as a consequencethe blood pressure falls. This in its turn is said by many authors to cut downthe supply of blood to the brain, to produce in short a condition of cerebralanaemia. Howell has observed the volumetric variations of the hand and the lowerpart of the forearm in sleep by means of the plethysmograph, and has found
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Fig. 299.—Cur\e roiiri-.stntiiig tlic depth of sleep, after Piesbergen. Tlic abscissa; represent hours. that the amount of blood in the part increases gradually from the beginning ofsleep and reaches its maximum within one to one and three-quarter hours. Itremains at this level until about three-quarters of an hour before awakeningand then falls rather rapidly to the end of sleep. The inception of sleep is favored by cutting off the sensory stimuli, espe-cially if tlie attention be not kept aroused by any active mental processes.Striimpell has rept)rted a case in which the patient became blind in one eyeand deaf in one ear merely by stnp))ing all cutaneous sensations. As soon asthe good eye was closed and the functional ear was stopped he fell asleep. Sleep does not depend entirely upon processes going on in the cerebral cor-tex, for as mentioned at page 623 a change from the sleeping to the wakingcondition and vice versa can be observed on decerebrated animals. (Perhaps the most sa

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