290 REPORTS ON THE STATE OF SCIENCE. 



from its ribs, still exhibits a blaze current, while its capacity for evolv- 

 ing HON under the influence of an anaesthetic has disappeared. The 

 colour of such a leaf is changed from yellow to brown by the action 

 of chloroform vapour. 



The Effect of Climate upon Health and Disease. — Fourth Report of the 

 Committee, consisting of Sir Lauder Brunton (Chairman), Mr. J. 

 Barcroft and Lieut.-Colonel K. J. S. Simpson (Secretaries), 

 Colonel Sir D. Bruce, Dr. S. G. Campbell, Sir Kendal Franks, 

 Professor J. G-. McKendrick, Sir A. Mitchell, Dr. C. F. K. 

 Murray, Dr. C. Porter, Dr. J. L. Todd, Professor G. Sims Wood- 

 head, and the Heads of the Schools of Tropical Medicine of Liver- 

 pool, London, and Edinburgh. 



The work produced by the Committee has consisted in a series of 

 observations carried out in the island of Teneriffe on the subjects of 

 the effect of altitude and solar radiation upon the organism. The 

 Committee are only prepared to report upon the first of these subjects 

 this year. The work was carried on at three stations, the altitudes 

 of which were — sea-level, 7,000 feet, and 11,000 feet respectively. 



The dissociation curves of four members of the party were studied, 

 two completely. 



The figure shows those of B and D. D's curves were investigated 

 at a constant C0 2 tension equal to that of his alveolar air at the sea- 

 level (41 mm. of mercury). At different altitudes it was found that 

 the affinity of the blood for oxygen decreases progressively as the 

 altitude increases. In point of fact D's CO a tension became progres- 

 sively lower as the altitude increased, and therefore another series of 

 curves was delineated in which the C0 3 tension was that of the 

 alveolar air at the altitude in question. These curves coincided with 

 one another and with the sea-level curve (D). The probable explana- 

 tion of these facts is that as the altitude increases the carbonic acid is 

 replaced in the blood by some most volatile acid, such as lactic acid, 

 and that the total effective concentration of acid is the same through- 

 out. The case of B. is somewhat different. B's dissociation curve 

 remained the same throughout, as also did the carbonic acid in his 

 alveolar air. Hence in his case also the total concentration of acid 

 in the blood remained unaltered. The further question arises, Is it 

 possible to explain the difference between the two types of reaction? 

 In the first place, as shown by the figure, B's curve at the sea-level 

 was somewhat different from that of D. The difference indicates a 

 greater alkalinity in B's blood. Titration bore out this indication. In 

 the second place, considerations based upon his respiratory quotient 

 require that in proportion as the C0 2 tension in D's alveolar air was 

 lower at 11,000 feet than in that of B, so D's oxygen tension was 

 higher than that of B. Actual analysis showed this to be true. At 

 11,000 feet D had an oxygen tension of 63 mm. and B of 49 mm. 

 In the third place, Krogh has shown that the oxygen tension in the 



