758 TRANSACTIONS OF SECTION f. 



actually exposed for about 30 minutes above +60 lb., and virtually exposed 

 about 50 minutes. From +60 lb. they were safely decompressed, six experiments. 



M. Greenwood was once decompressed safely from +92 lb. in 2 hours 17 

 minutes, after actual exposure above +75 lb. for about 30 minutes, and virtual 

 exposure for about 55 minutes. 



Hersent safely decompressed men after exposures of one hour in 

 26 minutes from + 2£ atm. ; in 46 minutes from +3 atm. ; in 60 minutes from 

 +3^ atm. ; in 77 minutes from +4 atm. ; in 100 minutes from +4^ atm. ; in 

 150 minutes from +5 atm. ; in 183 minutes from +5£ atm. Hersent safely used 

 a method which is theoretically the worst — viz., +5 to +4 atm. in 45 minutes; 

 +4 to +3 in 35; +3 to +2 in 30; +2 to +1 in 20, +1 to +0 in 15. 



Damant and Catto were safely decompressed several times after short ex- 

 posures by the stage method of the Admiralty Committee, e.g., in 51 minutes, 

 after 12 minutes, at +80 lb. ; in 90 minutes, after 29 minutes, at +80 lb. ; in 

 50 minutes, after 6 minutes, at +93g lb. 



These few high-pressure observations on men show that the stage method 

 can be used safely after short exposures. The experience of divers has 

 proved that a short uniform decompression in 20 minutes or less can be safely 

 borne after exposure of not more than 15 to 20 minutes to +60 to +73 lb. — e.g., 

 Erostabe, Lambert. Much depends on the individual. They do not prove the 

 far greater risk of the uniform method as claimed by the Admiralty Committee. 



Conclusion. — One stage at +15 lb. would suffice for caisson workers up to 

 +50 lb. Exercise and oxygen can be used to shorten the pause at +15 lb. A 

 pause of 15 minutes at +10 lb. for +30 lb., and of 30 minutes at +15 lb. for 

 +45 lb. would probably suffice, so long as a medical lock for recompression is af 

 hand. 



2. The Cause of the Treppe. By Professor Frederic S. Lee. 



When the irritability of the excised muscle, as indicated by the threshold of 

 Stimulation, is determined at ihtervals throughout the course of the treppe it 

 is found progressively to increase. Moreover, the irritability of muscle, as 

 indicated by the threshold of stimulation, is increased by small quantities of 

 fatigue substances, such as carbon dioxide and lactic acid. Under the influence 

 of these same substances, also in small quantities, a muscle is able to perform 

 greater contractions than before. It is, therefore, believed that the treppe 

 represents increased irritability and actually increased working power, due 

 to the action of small quantities of fatigue substances, among which may be 

 included carbon dioxide, lactic acid, and possibly other compounds. The treppe 

 is the physical expression of augmented vital processes. 



According to Frohlich, on the other hand, the augmentation of working power 

 is not real, but only apparent. Fatigue begins with the commencement of the 

 series of contractions. It is manifested by a slowing of relaxation, a diminution in 

 the extent of contraction of the muscle elements, and a diminution in irritability. 

 The experimental results of the present author do not support Frohlich's theory. 



3. The Summation of Stimuli. 

 By Professor Frederic S. Lee and Dr. M. Morse!. 



Professor Lee has. found that muscle, when under the influence of small 

 quantities of fatigue substances, such as carbon dioxide and lactic acid, and 

 stimulated maximally, is abie to perform greater Contractions than before. Hd 

 has explained the treppe as the physical expression of augmented vital processe , s ( 

 which are represented by increased irritability and increased working powei\ 

 due to the action of small quantities of fatigue substances. This theory is now 

 extended to the phenomenon of summation of Stimuli. During the action of 

 sub-minimal stimuli the irritability of muscle increases. Moreover, when a 

 muscle is put under the influence of small quantities of carbon dioxide or lactic 



