384 RESPIRATION [OH. XXVI. 



which provides for the escape of the expired air. A bottle contain- 

 ing the anaesthetic is placed on the course of the delivery tube. 



Artificial respiration is sometimes necessary in man to restore 

 normal breathing, as for instance in those who are apparently dead 

 from drowning. In such cases speed in commencing the artificial 

 breathing, and perseverance in continuing the process are essential. 

 Many have been restored to life after the efforts have been continued 

 for an hour or more. It is now recognised that of the numerous 

 methods for performing artificial respiration, that recently introduced 

 by Schafer is the simplest, least injurious, and most effective. The 

 subject is laid on the ground in the prone position, with a thick 

 folded garment under his chest. The operator kneels by his side 

 or athwart him facing his head, and places his hands on each side 

 over the lower ribs. He slowly throws the weight of his body 

 forwards, and thus presses upon the thorax of the subject, and 

 forces air out of the lungs (fig. 302, A) ; he then gradually relaxes 

 the pressure by bringing his body up again, but without removing 

 his hands (fig. 302, B). This is repeated regularly at the rate of 

 twelve to fifteen times a minute until normal respiration begins, or 

 until all hope of restoration is given up. 



Ventilation. 



Some observers have stated that certain noxious substances are 

 ordinarily contained in expired air which are much more poisonous 

 than carbonic acid, but more careful researches have failed to sub- 

 stantiate this. If precautions be taken by absolute cleanliness to 

 prevent admixture of the air with exhalations from skin, teeth, and 

 clothes, the expired air only contains one noxious substance, and that 

 is carbonic acid. 



Absolute cleanliness is, however, not the rule; and the air of 

 rooms becomes stuffy when the amount of expired air in them is just 

 so much as to raise the percentage of carbonic acid to 0-1 per cent. 

 An adult gives off about 0-6 cubic feet of carbonic acid per hour, and 

 if he is supplied with 1000 cubic feet of fresh air per hour, he will 

 add 0-6 to the 0-4 cubic feet of carbonic acid it already contains; in 

 other words, the percentage of that gas will be raised to 0-1. An 

 hourly supply of 2000 cubic feet of fresh air will lower the percentage 

 of carbonic acid to 0-07, and of 3000 cubic feet to 0-06, and this is 

 the supply which is usually recommended. In order that the air may 

 be renewed without giving rise to draughts, each adult should be 

 allotted sufficient space in a room, at least 1000 cubic feet. 



Leonard Hill has recently stated that the effects of bad ventilation 

 are not so much due to changes in the chemical composition of the 

 air, as to the absence of movement in the air ; moving air has a 

 stimulating, and still air a depressing effect. 



