Rejiex Times in the South African Clawed Frog. 



31 



wind. The evaporative cooling power of the wind may, therefore, have had 

 an effect. 



The retardation of growth cannot be attributed to the shaking produced by 

 the motor, because seeds sheltered from the wind, but submitted to the shaking, 

 grew as well as the control seeds. 



The conclusion is reached that the stunting effect produced by wind is not 

 only due to a less favourable wetting, but to greater cooling. The growing 

 point may be robbed by wind of heat which is produced in the cellular growth 

 processes — heat which facilitates growth. 



I am much indebted to Mr. E. H. Davis, of Messrs. Siebe Gorman, Ltd., 

 who gave me facilities for carrying on this research at a time when the 

 National Institute of Medical Eesearch was being used as a War hospital. 



Rejiex Times in the South African Clawed Frog. 

 By W. A. Jolly. 



(Communicated by Prof. E. Sharpey Schafer, F.R.S. Received November 1, 1920.) 

 (From the Physiology Depai'tment, University of Cape Town.) 



This investigation was undertaken with the object of determining the times 

 of certain reflexes in a species of frog which has not, so far as I know, already 

 been used for the purpose, viz., the South African clawed frog or toad 

 {Xenopm Icevis, or an allied species), and by analysing these times to obtain a 

 measure of the delay in transmission of the reflex impulses in the spinal cord, 

 or " synapse time." Spinal and decerebrate animals have been used as well 

 as the intact frog. Einthoveu's string galvanometer was employed to 

 indicate the beginning of activity in the limb muscles. 



It seemed desirable to eliminate, as far as possible, everything that would 

 tend to introduce doubt into the interpretation of the_records, even at the 

 cost of making the experiments more troublesome to carry out. For this 

 reason no strychnine or other drug was used. The spinal and decerebrate 

 preparations were kept alive before experiment until the wounds were 

 entirely healed and the frogs appeared to be in thoroughly good condition. 

 Records were then taken from day to day, and the influence of temperature 

 and of the period of survival after operation was studied. Any operative 



