EFFECT OF ADRENIN UPON RATE OF LOCOMOTION. 165 



could not be kept in a straight path, and the larger posterior 

 parts moved too slowly in the beginning for any effect of adrenin 

 to be noticeable. It may be noted in this connection that 

 Gruber (3) obtained the same results with denervated vertebrate 

 muscle as with normal nerve-muscle preparations. 



Before concluding it may be of interest to mention the results 

 of a few experiments upon toad larvae. Only fifteen tadpoles 

 were used; and although the results obtained are by no means 

 conclusive they indicate several possibilities which may lead to 

 further investigation. Tadpoles of two ages were used, measur- 

 ing during the period of experimentation from 8 to 10, and 14 to 

 1 6 mm. in length. The rates of locomotion were determined by 

 the time needed to swim around a circular track .7 cm. wide 

 and 25 cm. in circumference. This method was suggested by the 

 habit frequently observed in normal tadpoles of swimming around 

 the sides of the bowls in which they are kept. 



Very young tadpoles seemed unaffected by a solution of 

 adrenin crystals I : 10,000, although older ones showed some 

 response. Solutions of I : 1,000 strength were therefore used, 

 and a slight decrease in rate was obtained. As with Planaria, 

 this slowing was again due to a greatly increased excitability 

 which made sustained action impossible. After exposure to the 

 extract the tadpoles reacted spasmodically to mechanical stimula- 

 tion, swimming about in t a highly excited state for a short time; 

 but they soon become exhausted and unable to react until after 

 a period of rest. This state of excitability followed by exhaustion 

 was more pronounced in the larger than in the smaller tadpoles, 

 probably indicating an increased sensitivity. 



Adrenalin chloride of the same strength had a very powerful 

 effect, producing absolute paralysis of movement in less than a 

 minute. If the animals were removed at once, however, and 

 allowed to recover in water for an hour, the same excitability 

 and lack of endurance was noted as with the solution of adrenin 

 crystals. This seems to bear out the suggestion made at the 

 beginning that it is the chloretone in the preparation which 

 causes the immediate stupefying effect. The same paralysis, 

 moreover, is produced by a solution of chloretone of strength 

 equal to that contained in the adrenalin chloride solution. 



