396 PHYSIOLOGY. 



escape the effects of a want of oxygen in the blood? To overcome 

 this diminished absorption of oxygen Nature adapts itself by increas- 

 ing the number of red corpuscles in the blood. Then the increased 

 amount of haemoglobin in the blood can take up more oxygen, and 

 thus overcome the effects of a rarefied air. 



Ventilation. Let it suffice here to recall that the problem of 

 ventilation consists in maintaining, in more or less closed spaces, the 

 normal composition of the atmospheric air. Not only this, but to 

 counteract the incessant modifications the respiration of man or of 

 animals makes this medium undergo. For these purposes it is 

 important that the ventilation should be very active. 



It has been established that, for closed spaces intended to receive 

 healthy persons, it suffices that the ventilation furnish 1,000 cubic 

 feet of new air per person per hour. This is not sufficient for hos- 

 pitals which contain sick persons, where more abundant and vitiated 

 emanations are received by patients less fitted to react against 

 their influence. Those hospitals which receive 3,000 cubic feet of 

 fresh air for each sick person hourly are free from odor. 



A healthy adult gives off about 0.6 cubic feet of carbonic acid 

 per hour. If he be supplied with 1,000 cubic feet of fresh air per 

 hour he will add 0.6 to the 0.4 cubic feet of carbonic acid it already 

 contains. That is, he raises the percentage to .01. 



Pharmacological. The increase of pressure in the pulmonary 

 circulation and a simultaneous decrease of arterial tension in the 

 systemic circulation by amyl nitrite are due either to a contraction 

 of the pulmonary vessels or to a weakness of the left ventricle, and 

 as a consequence a backing up of blood in the left auricle. Nitro- 

 glycerine acts like nitrite of amyl. Aconite lowers the pressure in 

 both the pulmonary and systemic circulations, due to a weakening 

 of both sides of the heart. Ergot constantly causes a marked 

 increase of pulmonary arterial tension, with a primary decrease of 

 aortic pressure, hence is not useful in pulmonary haemorrhage. 

 Digitalis, strophanthin, and adrenal extract increase the tension in the 

 systemic circulation, leaving the pressure in the pulmonary circulation 

 unchanged. It is singular that the adrenal extract should so greatly 

 affect the systemic pressure and not the pulmonary, whilst ergot acts 

 reversely augments the pulmonary pressure more than that of the 

 aortic system. These facts show the independence of the pressure in 

 the pulmonary vessels to the tension in vessels of the systemic 

 circulation. 3 



sTigerstedt, Ergebnisse der Physiologic, 1903. 



