On Relationship between Staircase phenomenon and fatigue. 297 



as possible and without previously pithing the frogs. The 

 roof of the skull was removed by means of a fine pair of 

 bone-forceps and the brain, from the root of the olfactory 

 nerves down to the tip of the fourth ventricle, was removed, 

 the whole Operation taking not more than from 2 to 3 minutes 

 for eaeh frog. The brains were divided longitudinally and the 

 two parts of each were placed m a 2®/q Solution of Neutral 

 red for from 4 to 5 minutes; they were then taken out and 

 placed in Ethyl Acetate; the two brains were placed in the 

 neutral red Solution exactly at the same moment, so that any 

 differences in the depth of stain imparted during the process 

 must have been due to previous treatment. 



After 5 minutes there was a distinct difiference between 

 the cut surfaces of the two brains; the cut surface of the brain 

 of the frog which had been stimulated was deep red, that of 

 the brain of the unstimulated frog was pink. In 25 minutes 

 the difiference was very marked; viewed through the hquid, 

 which was stained somewhat yellow, the cut surface of the 

 brain of B was red while that of the brain of A was pale 

 yellowish pink. After 1 hour the cut surface of the brain A 

 was colourless and that of the brain B was reddish pink. 



Evidently the brain becomes more acid as a result of 

 prolonged Stimulation of sensory nerves. Exactly the same 

 method may be used with success to demonstrate the develop- 

 ment of acid in muscular tissue as a product of fatigue, only 

 in this case the difiference is more readily brought out if the 

 Ethyl Acetate be previously rendered faintly alkaline (20 ccm 

 Ethyl Acetate plus ^f^^ ccm ^/^^ KOH); in the stimulated 

 muscle the acit formed neutralises the alkali and, the neutral 

 red being mainly in the form of the Compound with acid 

 remains in the watery layer, that is, in this instance, in the 

 muscular tissue, while in the unstimulated muscle, the reaction 

 of the watery layer being neutral or faintly alkaline, the neu- 

 tral red is mainly present in the form of the free base and 

 therefore passes out into the Ethyl Acetate layer. 



The experiment with Frog's brains was repeated a number 

 of times, in some instances te anal region, in others the 

 thighs or abdominal waUs being chosen as the region {or Stimu- 

 lation; in every case results similar to that described above 



