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316 J. A. macwilliam 



conditions in question in sleep — 1, sound sleep with lowering of pres- 

 sure, 2, disturbed sleep, dreaming, etc., which may be attended by- 

 remarkable elevations of pressure, e.g., systolic pressure raised from 

 125 to 182 mm., or from 130 to 200, etc.; diastolic pressure raised from 

 75 to 105 mm., etc. These changes were much greater than were 

 induced in the same individuals by moderate exertion (cycling, walk- 

 ing, stair climbing, etc.) straining abdominal efforts, dose of atropin 

 to remove vagus control over the heart, mental excitement, etc. In 

 view of the rapid development of such changes in sleep, especially in 

 dreams of motor effort, nightmares, etc., it is evident that a formidable 

 strain — harmless in the young and healthy person — may thus be 

 thrown on the weak points of the circulatory system, whether these be 

 cardiac with susceptibility to anginal attacks or to ventricular fibril- 

 lation and sudden death, or arterial with risk of hemorrhages, cerebral 

 (especially in the recumbent posture), gastro-intestinal or pulmonary'-. 

 The conception of sleep as a period of quiescence and recuperation has 

 thus to be qualified by the contingency of disturbed sleep with active 

 calls on the nervous system, the heart and the blood-vessels. The 

 mechanism of the rise of pressure in disturbed sleep differs in some 

 respects from that present in ordinary muscular exertion, since in the 

 former the pumping action of working muscles, greatly augmenting 

 the venous return to the heart, is absent. The above-mentioned dis- 

 turbances may occur during disturbed sleep when there is after awaking 

 no recollection of definite dreaming. 



High blood pressure. Notwithstanding the very large amount of 

 attention that the subject has received the causation and mechanism 

 of persistently elevated blood pressure, whether in the form of simple 

 or essential hypertension (the hyperpiesis of Clifford Allbutt (3)) or 

 in association with kidney lesions, remain unexplained. While there 

 is general agreement as to the existence of excessive pressures apart 

 from an3^ recognisable renal lesions and in the absence of any sign of 

 functional inadequacy as tested by the modern methods for estimating 

 renal efficiency, it is also clear from the evidence available that the 

 significance of hypertension is greatly influenced by the co-existence of 

 renal inadequacy, the latter giving a sinister aspect to the condition 

 and seriously altering the prognosis. While there has long been a 

 strong presumption from the clinical side that, 1, toxic substances, 

 probably protein derivatives, are at work, whether a, absorbed from 

 the alimentary canal (pressor amines, etc.), or h, products of microbic 

 infection, or c, abnormal metabolism; or 2, that endocrine derangements 



