Brain and the Conditions of Recovery after Compression. 19 



Onz 5' 



FIG. 7. 



Time in Seconds. 



30" On 3" 3" 



50" 



Ex. a. 



Ex.b. 



Thus we see that, out of three experiments (246, 25c, and 266) in 

 which both external jugulars were blocked, in only one (viz., 24&) 

 is there an appreciable increase in recoil. (In this case, to be sure, 

 the internal j ugulars were also included, but, in the light of experi- 

 ment 24a, I cannot believe that these insignificant veins are a factor 

 worth considering.) Experiments 25a, 256, and 26a^show no increase 

 of elasticity on blocking one or both superior cerebrals in any one of 

 the cases, and hence are in strong contrast to 23a, in which the 

 increased recoil is quite noticeable. This last experiment is also of 

 importance, from the fact that the rise in venous pressure accompany- 

 ing the increase in elasticity was actually measured, and it shows 

 what a very considerable rise in the pressure (double the normal in 

 this case) is necessary to influence elasticity at all, and is an indica- 

 tion of how far we may disregard the effect of small changes of 

 venous pressure as factors vitiating results set forth in former 

 sections of this paper. 



o 2 



