101 



Eelations of the Period of Sleep to Some Diseased 

 Conditions. 



In accordance with the accepted view that the vital 

 activities, as indicated by heart action, respiration, blood 

 pressure, temperature, and general metabolism, reach their 

 low-water mark in the early hoiiis of the morning, it is 

 easily intelligible that death from illnesses involving pro- 

 gressive exhaustion and a gradual running down of the 

 machinery of life should often take place in that period. 

 Statistics are available which bear this out. Thus 

 Schneider (Berlin), in a total of nearly 58,000 deaths, found 

 that deaths were most common between 4 and 7 a.m. 

 Watson and Finlayson (Glasgow), dealing with records of 

 nearly 14,000 deaths, fixed the highest mortality between 

 5 and 6 a.m. 



Many phenomena of disease, aggravation of morbid con- 

 ditions and symptoms in the night, can be brought into 

 relation with the general lowering of vital activities during 

 sleep — for example, some respirator}^ troubles which may 

 in some cases be associated with the depression in respira- 

 tion naturally occurring in that period, the reduced sensi- 

 tiveness of the respiratory centre to the normal excitation 

 by CO^ with the consequent modification in the state of the 

 blood, heightening of the grade of acidosis which may be 

 present, development of Cheyne-Stokes respiration, etc., 

 often associated with attacks of severe dyspnoea, etc. 



Incidence of Haemorrhages, Anginal Attacks, and 

 Sudden Death in the Night. 



In contrast with the associations of depressed functions 

 during sleep as affecting some of the manifestations of 

 disease there is another class of phenomena for which a 

 different interpretation is required, for they obviously do 

 not lend themselves to ex])lanation by the lowered vital 

 activities of nightly rest and sleep. 



In connexion with the subject of haemorrhages of various 

 kinds and their times of occurrence and mechanism, ques- 

 tions arise. The time incidence of many vascular ruptures 

 is naturally accounted for by the conditions prevailing at 

 the moment of their occurrence — rise of blood pressure and 

 increased stress on the walls of the vessels determining rup- 

 ture at the weakest part — for example, muscular effort, 

 the influence of gravity in cei'tain postures, abdominal 

 straining, etc. 



But why should a weakened vessel give way during the 

 period of nocturnal rest and sleep, since a lowered blood 

 pressure is naturally protective against rupture? Why 

 cerebral haemorrhage should frequently occur in the night 

 and in sleep is a question that was asked long ago by Sir 

 Samuel Wilks and apparently never answered. In view of 

 the lowering of blood pressure and a diminished blood flow 

 through the brain in sleep, why should a cerebral vessel 



