156 J- Lindhard. 



they chose a mountain station (Chasseral), where the importance of 

 these other factors might be considered as relatively slight, in order 

 to obtain the main influence pure; but as the height was but small 

 (ca. 1600 m.), the experiments are not illustrative of possible changes 

 owing to low air-pressure. 



In opposition to other physiologists who have made mountain 

 experiments. Mosso ^ maintains that during rest there is no increase 

 in the production of carbonic acid at high altitudes. His results are 

 however too few and vary too much to be able to form a basis for 

 his conclusions. 



Heller, Mager & Schrötter'^ also consider the lack of oxygen 

 as the cause of changes in the respiration at high altitudes. In ad- 

 dition to an anoxyhaemia absoluta {anoxyhaemia barometrica, Jour- 

 danet), they also postulate an anoxyhaemia relativa, which is only 

 active during work, and not during rest; the latter can be promoted 

 by the climatic conditions: temperature, wind, absolute dryness, 

 "gewiss auch das Licht". 



Speck -^ cites a number of the older authors Avith regard to the 

 effect of light on metabolism, especially Moleschott, who found a 

 no slight increase of metabolism in frogs under the action of light; 

 the increase is proportional to the strength of the light and is due 

 partly to its action on the skin, partly through the eye. Speck 

 points out that Moleschott's results are far too variable to form a 

 basis for conclusions, and maintains especially, that Moleschott 

 like other authors has not paid attention to the more active muscular 

 movements in the light. Speck shows from his own experiments, 

 that the light cannot be credited with any importance in increasing 

 the metabolism, but perhaps that it has a stimulating effect on the 

 total volume of air respired with the resulting increased absorption 

 of oxygen and separation of carbonic acid. 



Speck has most probably not estimated the last-named condition 

 at its true value; but it plays a very subordinate part in this con- 

 nection. The arrangement of his experiments is not satisfactory on 

 the whole, and especially as regards the action of light it is hardly 

 to be expected that this would come into consideration. Speck has 

 not exposed himself at all to the chemical rays of light; he remained 

 in his working-room and there carried out a series of experiments 

 of quite short duration, alternately with open and with blind-folded 

 eyes. It is not to be expected that he would come to any result by 

 this method; when he nevertheless believes that he has found in- 



1 1. c, Chap. XV. 



2 Zeitschr. f. klin. Medizin. Bd. 34, 1878. 



^ Physiologie des menscli. Athmens. Leipzig 1892, Chap. XL 



