292 REPORTS ON THE STATE OP SCIENCE. 



The degree of saturation of the blood with oxygen at the above 

 tensions may be read from the figure. The point of interest is that, 

 at rest (i.e., using about 300 c.c. of 2 per minute), B's blood and 

 D's are about equally saturated-. Hence, as B was careful not to 

 take much exercise, his blood has had no occasion to compensate, he 

 was in as strong a position as D, who had compensated. On the other 

 hand, were increasing quantities of exercise taken, and increasing 

 quantities of oxygen absorbed, B would be more and more at a dis 

 advantage. These facts form at least an intelligible reason why B 

 should have suffered from mountain sickness when he attempted to 

 take exercise at 11,000 feet, whilst D did not. 



Mental and Muscular Fatigue. — Interim Report of the Committee, 

 consisting of Professor C. S. Sherrington (Chairman), Mr. W. 

 MacDougall (Secretary), Professor J. S. MacDonald, and Mr. H. 

 Sackville Lawson. 



Professor Macdonald, of Sheffield, has been engaged especially on 

 the physiological aspects of muscular fatigue as studied in isolated 

 muscle preparations. A report of his results is presented herewith. He 

 separates the phenomenon of contracture as a fatigue effect from that of 

 diminution of the height of the contraction. He draws attention to the 

 fact that fatigue muscle will do an amount of work similar to the 

 amount furnished by a fresh muscle, with less attendant production oi' 

 heat. 



Mr. H. S. Lawson, of Wolverhampton, has worked on the examina- 

 tion of fatigue in schools, and has had a number of school teachers 

 engaged in the observations. 



It is urgently desirable that the Committee should be reappointed 

 for another year in order to carry their investigations further. 



Interim Report on Muscular Fatigue. June 1909. 

 By Professor J. S. MacDonald. 



Repeated excitation of exercised frog's muscle leads finally to a 

 complete stage of exhaustion, during which a maintained state of slight 

 contracture is present unbroken by any new contractile responses to 

 continued stimulation. Prior to reaching this stage, the muscle yields 

 contractions steadily diminishing in height and increasing in duration. 

 These two modifications do not follow the same law of development. 

 It is possible thus to secure a maximal degree of the one associated with 

 a minimal degree of the other. Thus also the change in height of the 

 contractions is arithmetically progressive, whereas the change in dura- 

 tion, increasing at first slowly, later proceeds at greatly increased pace. 

 The later stages of this rapid development may be masked when the 

 muscle is made to lift a maximal load, and such conditions may give rise 

 to the still more complex appearance of a contraction-time, increasing 

 at first and later diminishing. 



