158 IRRITABILITY 



amounts to about .5-1 second; on the stimulation of the trige- 

 minus produced by blowing on the cornea on the other hand, 

 it is somewhat shorter, less than .25 seconds. Zwaardemaker^ 

 also was able to demonstrate an analogous refractory period for 

 the swallowing reflex of the cat. Further a refractory period 

 was found and closely analyzed by Verworn^ for the reflexes in 

 the spinal cord of the strychninized frog. Dodge^ found a refrac- 

 tory period in the knee jerk reflex of man. Gotch and Burch* 

 showed, by two induction shocks following each other in quick 

 succession, a refractory period of the nerve, which is char- 

 acterized by its extremely brief duration. They found, depending 

 upon the temperature, a period of nonirritability of .001-.008 

 seconds after every stimulus. The investigations of Miss 

 Buchanan^ lead us to conclude that there is a refractory period 

 for the cross striated skeletal muscle. Miss Buchanan stimulated 

 the muscle at times through the nerve, at other times directly 

 after elimination of the nervous element, with very frequent 

 electrical stimuli (about 1000 in the second) and found by means 

 of the capillary electrometer a rhythmical reaction of the muscle 

 of about 50-100 excitation shocks per second. Likewise the 

 Ritter tetanus produced by the breaking of an increasing current 

 proved to be a rhythmical reaction of an analogous nature. In 

 a more direct manner Keith Lucas^ has determined the refractory 

 stage for the musculus sartorius of the frog. He allowed two 

 induction shocks to act successively on the muscle at intervals 



1 Zwaardemaker : "Sur une phase refractaire du reflex deglutition." Arch, inter- 

 national de physiologie Vol. I, 1900. 



2 Max Verworn : "Zur Kenntniss der physiologischen Wirkungen des Strychnins." 

 Arch. f. Anat. u. Physiol, physiol. Abth., 1900. "Ermiidung Erschopfung und Erholung 

 der nervosen Centra des Ruckenmarks." Ibidem, 1900. "Die Biogenhypothese." 

 Jena 1903. "Die Vorgange in den Elementen des Nervensystems." Zeitsch. f. allgem. 

 Physiologie Bd. VI, 1907. 



3 Dodge: "A systematic exploration of a normal knee jerk, its technique, the form 

 of the muscle contraction, its amplitude, its latent time and its theory." Zeitsch. f. 

 allgem. Physiol. Bd. XII, 1911. 



A Gotch and Burch: "The electrical response of nerve to two stimuli." Journ. of 

 Physiology, Vol. XXIV, 1899. 



5 Florence Buchanan: "The electrical response of muscle in different kinds of per- 

 sistent contraction." Journ. of Physiology, Vol. XXVII, 1901-1902. 



6 Keith Lucas: "On the refractory period of muscle and nerve." Journ. of Physiol- 

 ogy, Vol. XXXIX, 1909-1910. 



