EFFECTS OF DEPRIVATION OF OXYGEN 197 



(as indicated by an asterisk on the graphs) a noticeable dis- 

 turbance usually results, but this is usually quickly overcome. 



In those cases in which the rate of improvement is rapid; 

 the curve of performance reaches a level rather quickly; and such 

 subjects usually show a definite deterioration when the oxygen- 

 content is depleted to a point between 15 and 12 per cent. In 

 many subjects, this disturbance is compensated for by an in- 

 crease of muscular activity. The compensation may be partial, 

 as in no. 6877; complete, as in no. 6864; or excessive, as in no. 

 6924. In some subjects the tendency is not apparent. 



Occasionally, as in no. 6889, the increase of " voluntary" 

 effort due to the diminution of apprehension, distraction of 

 surroundings, etc., and the increase of interest is so great that 

 the performance steadily improves in spite of the deleterious effect 

 of depletion of oxygen, until the subject approaches cardiovas- 

 cular collapse. In this connection, it may be remarked that one 

 of the most frequently noted effects of diminution of the oxygen- 

 supply, is a constriction of the field of attention, which facilitates 

 the application of effort exclusively to the task in hand. If 

 the task is sufficiently simple, improvement in performance may 

 result. 



A brief comment is presented with the graphic record in each 

 case, and should assist materially in interpretation of the record. 



The reader is earnestly cautioned against drawing conclusions 

 from superficial inspection of the graphs. Contrary to the first 

 visual impressions, the graphs do not give a quantitative indi- 

 cation of the extent of deterioration of performance. This fact 

 will be made clear by consideration of the following facts : 



1. It would be unfair to compare the performance of subjects 

 having different degrees of dexterity, with a uniform standard. 



2. Owing to the fact that the subjects are available for only 

 a single sitting, it is not easy to establish a "normal" performance 

 for each one, with which the performance under diminished 

 oxygen may be compared. As was pointed out above, the 

 initial performance and also the rate of improvement with prac- 

 tice, depend so largely on variable and uncontrollable factors 

 that the subject's capability is not necessarily indicated by them. 



PSTCHOBIOLOOT, VOL. II, NO. 



