164 -ï- Lindhard. 



self-experiments, a difference that is partly counterbalanced by the 

 relatively long series of experiments. 



The material is in so far not "pure", as light-baths have been 

 included on a few days. The effect of these on the functions in 

 question here, seems however to be restricted to a few days and 

 affects the two series practically to the same extent, as there was 

 one light-bath in the short, two in the long series. Since, further, 

 the single elements of the experiment are subject from day to day 

 to influences of various kinds, temperature, air-pressure, individual 

 disposition, no inconsiderable fluctuations will also occur on this 

 account within the single columns. To unravel these in details 

 would, however, be too difficult, especially for one who has not 

 made or directed the experiments. 



As previously mentioned, Haldane has also indicated the exis- 

 tence of such a periodicity with respect to the alveolar carbonic 

 acid tension ^ He gives here : 



CO2 pressure 

 in mm. of mercury 



Thus the movement here also has the same dii^ection as in my 

 experiments; the difference, as we should expect, is somewhat less. 

 It must be remarked, however, that the cases are relatively few, 

 Avhich means so much the more as the values on which the aver- 

 ages are based, vary much more than mine. 



Apart from this there is only one extensive series of experiments 

 Avhich concerns the present subject. 



E. Smith fifty years ago carried out a very large number of 

 respiration experiments, partly to determine the amount of carbonic 

 acid produced in 24 hours, partly to investigate the yearly variation.' 

 He came to the following results ^. 



The respiration has a maximum in the spring and a minimum 

 in the autumn; it decreases in June, increases in October. The 

 reduction in summer amounts to according to the author: 



in the total volume of air respired 30 °/o 

 in the frequency 32 - 



in the production of carbonic acid 17 - 



1 The Journal of Physiology. Vol. XXXVII, Nos. Г)— 6, Decb. 1908. 

 - Proceedings of the Royal Society' of London. Vol. IX, 1859, p. (ill. Philosophical 

 Transactions. Vol. 149. II. 1859. 



