On Changes in the Sea and Their Relation to Organisms. 251 



Acidosis develops in the acclimatization to high altitudes and 

 persists some time after the descent, during which time the subject 

 feels more vigorous (Schneider). During acidosis the ventilation of 

 the lungs is increased to such an extent that the alveolar air is increased, 

 and therefore the O2 in the blood-plasma is increased and that in the 

 hemoglobin is increased if it is not already saturated. Increased 

 respiratory movements tend to increase the heart-rate and hence the 

 circulation, with better oxygen transfer to the tissues and increased 

 oxidation. This effect may be small, and may be too small to account 

 for the total increase in metaboUsm, but is worthy of consideration. 

 Rasmussen has shown mild acidosis in case of the hibernating wood- 

 chuck with very much lowered O2 tension of venous blood, but evi- 

 dently the sensitivity of the respiratory center falls during hibernation. 



It was shown by Warburg that the metabolism of sea-urchin eggs 

 may be stimulated, but these are to be considered irritable cells in the 

 same class with muscle. It may be that the metabolism of all cells 

 can be stimulated, but they are not equally sensitive. Changes in 

 hydrogen-ion concentration of the sea-water effective on sea-urchin 

 eggs are not nearly so effective on the cells of Cassiopea (possibly 

 because the pH of the sea- water changes before reaching the cells). 

 Benedict claims that the basal metabolism of the human body may be 

 stimulated, but it is difficult to estimate basal metaboUsm on account 

 of the unavoidable activity of some excitable organs. Cutting the 

 nerves is of no advantage, since Langley and Itagski showed that the 

 oxygen consumption of denervated muscle is much greater than that 

 of normal resting muscle. What cells are stimulated in Benedict's 

 experiments is not clear. He adds that changes in the pulse-rate 

 accompany changes in the basal metabolism, and thus admits that 

 irritable cells of the complex neuro-muscular organization of the body 

 are concerned in the phenomenon. If the respiratory or vasomotor 

 centers are concerned in the increased metabolism, O2 tension in the 

 tissues may be a factor. Verzar showed that resting muscle and active 

 heart use more oxygen when there is more in the blood. The sub- 

 maxillary gland used oxygen at the same rate in all experiments, but 

 suffocation of the animal occurred when the oxygen tension in the gland 

 was about 40 mm. Rasmussen (see also Dubois) has shown that the 

 oxygen concentration of the venous blood of marmots (woodchucks) 

 is lowered during hibernation, although the oxygen capacity of the blood 

 remains the same. This shows that the O2 tension of the blood is 

 lowered both by fall in concentration and temperature, and this may be 

 a factor in the lowered metaboUsm. The O2 concentration of the arte- 

 rial blood is not reduced, but the rate of blood-flow is very much reduced, 

 so that less oxygen is carried to the tissues. 



