102 PHYSIOLOGICAL CHEMISTRY. 



the elimination of carbon dioxide and the combustion of the sugar 

 of the blood, was lowered. By raising the oxygen pressure of the 

 air to 3 atmospheres the amount of oxygen contained in the blood 

 is somewhat increased. It seems that the amount of oxygen which 

 is here taken up corresponds to that quantity which is simply ab- 

 sorbed by the blood at that pressure. 



It is also of special interest to know to what extent the partial 

 pressure of the oxygen of the air can be lowered without causing any 

 injurious action or danger to life. A great many observations have 

 been made on this subject, partly on man (P. BEET, SIVEL and 

 CROCE-SPINELLI, LEBLAK c, and others) and partly on animals (by 

 W. MULLER, HOPPE-SEYLER, STROGANOW, BERT, FRIEDLANDER 

 and HERTER, FRANKEL and GEPPERT). From these observations 

 it seems that the partial pressure of the oxygen in the atmosphere 

 may sink to one half without causing a disturbance. The respira- 

 tion is hindered by an oxygen tension of 7-8$ of an atmosphere, 

 and at a still lower tension a lowering of the temperature is ob- 

 served, lassitude, inability of muscular movement, and insensibility. 

 At an oxygen tension which corresponds to about 3-3.5# of an 

 atmosphere, death occurs. 



In regard to the amount of oxygen in the blood at lower air- 

 pressures, the observations of FRANKEL and GEPPERT on dogs must 

 be mentioned. At an air-pressure of 410 mm. mercury the amount 

 of oxygen in the arterial blood was normal; at an air-pressure of 

 378-365 mm. it was a little diminished, and only at a lowering of the 

 pressure'to 300 mm. was a marked decrease of the oxygen observed. 



The tension of the carbon dioxide in the blood has been deter- 

 mined in different ways by PFLUGER and his pupils, WOLFBERG, 

 STRASSBURG, and NUSSBAUM. According to the density method, 

 the blood is allowed to flow directly from the artery or vein 

 through a glass tube which contains a gas mixture of a known 

 constitution. If the tension of the carbon dioxide in the blood is 

 greater than the gas mixture, then the blood gives up carbon 

 dioxide; while in the reverse case it takes up carbon dioxide from 

 the gas mixture. The analysis of the gas mixture after passing 

 the blood through it will also decide if the tension of the carbon 

 dioxide in the blood is greater or less than in the gas mixture; and 

 by a sufficiently great number of determinations, especially when 



