THE EFFECT OF ADRENIN UPON THE RATE OF 



LOCOMOTION OF PLANARIA AND OF 



TOAD LARVAE. 



E. LUCILE MOORE, 

 BIOLOGICAL LABORATORY OF BRYN MAWR COLLEGE. 



In his investigation of the chromaffine system of annelids, 

 Gaskell (2) has pointed out the close morphological and physio- 

 logical relationship which exists between the chromaffine, the 

 sympathetic and the contractile vascular systems, wherever 

 these are found. He holds that the presence of any systems 

 corresponding physiologically to the first two, necessarily implies 

 the presence of the third on which to act; and in support of this 

 view, he finds in the annelid group, in those forms which possess 

 a contractile vascular system, a cell which he considers the 

 common ancestor of the sympathetic and chromaffine systems. 

 If, therefore, the earliest indication of chromaffine tissue is found 

 among the annelida, it may be safely assumed that in the 

 platyhelminth group in which there is no contractile vascular 

 system, there is nothing comparable to the adrenin-producing 

 cells of higher forms. The effect of adrenal extract is not, 

 however, confined to the regulation of the cardio-vascular 

 apparatus, although this seems to be one of its chief functions. 

 Elliott (i) has definitely shown' that it affects other forms of 

 smooth muscle in a manner similar to the sympathetic nervous 

 system, causing either an excitation or an inhibition, according 

 to the nature of the sympathetic fibers supplying the tissue. 

 Its influence is, furthermore, not even limited to smooth muscle 

 for skeletal muscle is affected, also, as various investigators 

 have demonstrated. Is it possible, then, that this secretion of 

 the adrenal medulla exercises an influence upon the contracility 

 of the simple muscles of an organism such as Plan aria, which 

 does not itself manufacture adrenin? 



Bands of circular, longitudinal and diagonal muscles are found 

 in the body wall of planarians; and it is by means of these that 



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