THE ADRENAL BODIES 181 



sympathetic nerve endings. It has been shown that in 

 Mammalia, if the vagi have first been paralyzed with atropine, 

 adrenal extract produces an augmented systole and acceleration 

 of the heart. Both of these effects of adrenin may be abolished 

 by the injection of large doses of apocodeine. Thus, Dixon 

 found that in a cat c.c. of a 1 in 30,000 solution of adrenin 

 increased the heart-rate from 92 to 211 per minute. After 

 the injection of 100 milligrammes of apocodeine the same 

 injection of adrenin now only increased the rate from 93 to 

 101 per minute. A further injection of 200 milligrammes of 

 apocodeine was then administered, and caused the rate of the 

 heart to diminish to 87 per minute. Adrenin now, even in 

 large doses, produced no acceleration, and there was no augmen- 

 tation of the systole. Dixon therefore concludes that the 

 whole effect of adrenal extract on the heart is a stimulation of 

 the sympathetic nerve endings. Similarly, the vasomotor 

 nerve endings are paralyzed by apocodeine, and after the 

 administration of this drug no vasoconstriction can be induced 

 by means of adrenin. 



The addition of adrenin to any of the ordinary perfusion 

 fluids enables the heart to maintain its activity over much 

 longer periods of time. The time may be quadrupled by such 

 addition (Burridge). 



This view, that adrenin acts on nerve endings, is supported 

 by the observations of Macfie, who found that extracts of the 

 adrenal and other tissues are without effect upon the embryonic 

 heart, upon leucocytes, and upon cilia. Again, the work of 

 Brodie and Dixon, who find that there are no vasomotor nerves 

 for the pulmonary arterioles, and that adrenin, when perfused 

 through the pulmonary vessels, produces no constriction, is 

 decidedly in favour of the theory that the substance acts upon 

 jierve tissue only. 



On the other hand, Boruttau considers that the action is 

 direct on somatic muscle, since it occurs in curarized muscle, 1 

 and, according to Lewandowsky, the dilation of the pupil and 

 other eye effects are produced by a direct action of adrenal 

 extract on the constricted muscle. This was inferred from the 

 fact, referred to above (p. 179), that the extract is still effective 



1 It does not follow, of course, that, because a curarized muscle cannot 

 be excited through its nerve, therefore the whole of the nerve endings are 

 paralyzed. 



