xii RESPIRATION 



showing the non-existence of "vagus apnoea," 47. Afferent vagus excitations 

 coordinate the phases of breathing, 48. The depth and vigor of breathing de- 

 pend on the chemical stimuli to the respiratory center, 49. Effects of resistance 

 on the rhythm of breathing, 50. Artificial respiration and the vagus coordina- 

 tion of breathing, 50. Normal breathing and afferent nervous control, 53. 

 Evidence that the activity of the respiratory center depends on locally acting 

 chemical stimuli in the medulla oblongata, 53. Physiological significance of 

 this fact, 54. Fatigue of the respiratory center, 56. The breathing in "sol- 

 dier's heart" and allied conditions, 57. "Neurasthenia" and fatigue, 56. 

 Variations in individual susceptibility to fatigue of breathing, 57. 



CHAPTER IV. THE BLOOD AS A CARRIER OF OXYGEN 59 



General chemical properties of haemoglobin and oxyhaemoglobin, 59. Meth- 

 aemoglobin and its properties, 59. Action of ferricyanide in liberating oxygen 

 or CO from combination with haemoglobin, 60. Oxyhaemoglobin and CO 

 haemoglobin are molecular compounds, 61. The ferricyanide method of de- 

 termining the oxygen capacity of haemoglobin, 61. The oxygen capacity of 

 haemoglobin is exactly proportional to its coloring power, 61. The Gowers- 

 Haldane haemoglobinometer, 62. Normal variations in haemoglobin percentage 

 of blood, 63. Haemochromogen and its modifications, 64. Relation between 

 oxygen capacity and iron of haemoglobin, 64. Relation of haemochromogen 

 to haemoglobin, 66. Ferricyanide method for ordinary blood-gas determina- 

 tions, 66. Amount of available oxygen in human arterial blood, 67. Funda- 

 mental importance of the partial pressure of oxygen in the blood, 67. "Partial 

 pressures," "vapor pressures," "diffusion pressures," and "concentrations" of 

 substances in the living body, 67. Investigations of the laws of dissociation 

 of oxyhaemoglobin in blood, 68. Work of Paul Bert, Hiifner, Loewy and 

 Zuntz, Bohr, Barcroft, 70. Effects of salts, COz, and acids or alkalies, 72. 

 Physiological importance of the shape of the oxyhaemoglobin dissociation curve, 

 7 2.-^ Properties and dissociation curves of CO haemoglobin, 72. Nature of 

 alterations produced by CO2 on the dissociation curves of CO haemoglobin and 

 oxyhaemoglobin, 76. Relative affinities of oxygen and CO for haemoglobin, 

 74- Evidence of differences in the chemical structure of haemoglobin in differ- 

 ent individuals and species, 77. Use of haemoglobin for estimating partial 

 pressures of CO or oxygen, 79. Explanation of the peculiarities of the dissocia- 

 tion curve of oxyhaemoglobin in blood, 80. Equations for the dissociation 

 curves, 82. 



CHAPTER V. THE BLOOD AS A CARRIER OF CARBON 



DIOXIDE ........ 84 



Amount of CO 2 in normal human and dog's arterial blood, 84. Amounts in 

 simple solution and chemical combination, 85. The CO 2 is combined with 

 alkali as bicarbonate, 84. Why the bicarbonate dissociates appreciably with a 

 small fall in the partial pressure of CO 2 in the blood, 85. Haemoglobin and 

 other proteins act as acids in the living body, and do not combine with CO 2 , 

 though they play a most essential part in its carriage, 88. The dissociation 

 curve for CO 2 of human blood, 89. Constancy of this curve for the same indi- 

 vidual, and relative constancy in different normal individuals, 89. Evidence 

 that oxygen has a chemical action in liberating CO 2 in the lungs, 92. The de- 



