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THE POPULAR SCIENCE MONTHLY. 



in endless succession. In order to admit 

 of these changes, the auriculo-ventricular 

 valves, as has been stated, rise and fall like 

 the diaphragm in respiration ; the valves 

 protruding, now into the auricular cavities, 

 now into the ventricular ones. There is in 

 reality no pause in the heart's action. The 

 one movement glides into the other as a 

 snake glides into the grass. All that the 

 eye can detect is a quickening of the gliding 

 movements, at stated and very short inter- 

 vals. A careful examination of the sounds 

 of the heart shows that the sounds, like the 

 movements, glide into each other. There 

 is no actual cessation of sound when the 

 heart is in action. There are periods when 

 the sounds are very faint, and when only a 

 sharp or an educated ear can detect them, 

 and there are other periods when the sounds 

 are so distinct that even a dull person must 

 hear ; but the sounds and this is the point 

 to be attended to merge into each other 

 by slow or sudden transitions. It would 

 be more accurate, when speaking of the 

 movements and sounds of the heart, to say 

 they are only faintly indicated at one time, 

 and strongly emphasized at another, but that 

 neither ever altogether ceases. If, however, 

 the heart is acting more or less vigorously 

 as a whole, the question which naturally 

 presents itself is, How is the heart rested ? 

 There can be little doubt it rests, as it acts, 

 viz., in parts. The centripetal and centrif- 

 ugal wave-movements pass through the 

 sarcous elements of the different portions 

 of the heart very much as the wind passes 

 through the leaves : its particles are stirred 

 in rapid succession, but never at exactly the 

 same instant ; the heart is moving as a 

 whole, but its particles are only moving at 

 regular and stated intervals ; the periods 

 of repose, there is every reason to believe, 

 greatly exceeding the periods of activity. 

 The nourishment, life, and movements of 

 the heart are, in this sense, synonymous." 



Poisoning by Oxygen. M. Paul Bert, 

 whose observations upon the physiological 

 effects of high atmospheric pressure we have 

 already noted in the Monthly, communi- 

 cates to the Paris Academy of Sciences the 

 results of his observations on the toxic ac- 

 tion of oxygen. Placing sparrows in oxygen 

 under a pressure of 350 (that of the atmos- 



phere being represented as 100), he found 

 the birds seized with violent convulsions. 

 The same result followed when sparrows 

 were confined in common air under a press- 

 ure of 11 atmospheres. In oxygen, at 3 

 atmospheres' pressure, or in air at 22 at- 

 mospheres, the convulsions were extremely 

 violent and quickly fatal. The symptoms 

 in the latter case were these : Convulsions 

 set in after four or five minutes : in moving 

 about, the bird hobbles on its feet, as 

 though walking on hot coals. It then flut- 

 ters its wings, falls on its back, and spins 

 about, the claws doubled up. Death super- 

 venes after a few such spasms. 



The toxic dose of oxygen for a dog was 

 found to require, for convulsions, a pressure 

 of 350 in oxygen ; and a pressure of 500 is 

 fatal. The amount of oxygen in the arterial 

 blood of a dog in convulsions was found to 

 be considerably less than twice the normal 

 quantity. Hence the author's startling con- 

 clusion, that oxygen is the most fearful poison 

 known. 



Taking a dog in full convulsion out of 

 the receiver, M. Bert found the paws rigid, 

 the body bent backward in the shape of an 

 arch, the eyes protruding, pupil dilated, 

 jaws clinched. Soon there is relaxation, 

 followed by another crisis, combining the 

 symptoms of strychnine-poisoning and of 

 lockjaw. The convulsionary periods, at 

 first recurring every five or six minutes, be- 

 come gradually less violent and less fre- 

 quent. 



The author sums up his conclusions as 

 follows : 1. Oxygen behaves like a rapidly- 

 fatal poison, when its amount in the arte- 

 rial blood is about 35 cubic centimetres per 

 cent, of the liquid ; 2. The poisoning is 

 characterized by convulsions which repre- 

 sent, according to the intensity of the symp- 

 toms, the various types of tetanus, epilepsy, 

 poisoning by phrenic acid and strychnine, 

 etc. ; 3. These symptoms, which are allayed 

 by chloroform, are due to an exaggeration 

 of the excito-motor power of the spinal cord ; 

 4. They are accompanied by a considerable 

 and constant diminution of the internal tem- 

 perature of the animal. 



Infant Mortality. During the year 1868, 

 23,198 children under one year of age, 

 died by convulsions in England, the num- 



