EFFECTS OF DEPRIVATION OF OXYGEN 195 



different sets of test-material were derived by transliterating a 

 single set successively into the several codes. Thus the several 

 sets are also of approximately equal difficulty. The codes and 

 the test-material are reproduced in the appendix, with a brief 

 description of the method of preparation. 



Most of the tests were administered by Dr. Paschal according 

 to the following method: The subject is seated in front of the 

 Henderson rebreathing apparatus, behind an adjustable desk, 

 to which a large ruled card is secured, below a rack provided 

 for reception of the test-card. (Cf. appendix.) 



A sample test-card is placed in the rack, and the subject is 

 instructed to print 2 on the large ruled card the letters presented 

 in the given code to be substituted for the letters in the set of 

 test-material. 



The subject is informed that his performance depends on 

 both time and accuracy, and is measured by the number of letters 

 correctly substituted in a unit of time. 



The subject is then connected with the rebreather, and the 

 work is started. 3 



In the actual experiment, the following procedure is observed 

 with respect to presentation of the material: the test-card is 



2 It was observed during the exploratory work early in 1918 that handwriting 

 became more illegible than printing at advanced stages of oxygen-depletion 

 a fact which was later made the subject of a special study by Major John B. 

 Watson. In the opinion of Major Dunlap, who was in charge of the earlier work, 

 printing as a substitute for writing also tended to lessen the disadvantage of the 

 more clumsy and excitable subjects. 



3 In the earlier experiments the subjects worked up three sets of material 

 before the mouthpiece was inserted, and two additional sets after the mouth- 

 piece was inserted, and before rebreathing was commenced. In these experi- 

 ments the unmodified Henderson rebreather was used, and the duration of the 

 experiments was in many cases shorter than was desired. Through a method 

 devised by Capt. D. C. Rogers, of the section of psychology, it became possible 

 to increase the duration of the run as much as was desired, and to control, within 

 reasonable limits, the rate of consumption of oxygen. In these experiments the 

 mouthpiece was inserted and rebreathing was started before the first set of ma- 

 terial was presented; but during the first thirteen minutes all the oxygen con- 

 sumed by the subject was replaced as consumed, so that during that time the air 

 was normal with respect to oxygen-content. The position of the asterisk on the 

 graph and the accompanying note will indicate which type of rebreathing was 

 used in each case. 



