The Action of Adrenin on Veins. 



193 



(a) Veins Remote from the Heart. 



All the ring preparations of (large) veins which we have so far subjected 

 to the action of adrenin have responded by contraction. In the experiments 

 illustrated in the accompanying figures the magnification of movement was 

 the same in each case. Fig. 1 shows the contraction of an external jugular, 



Fig. 1. 



fig. 2 of a mesenteric, vein. In regard to the amount of contraction produced 

 they are, however, not comparable, because the temperature in the case of the 

 mesenteric vein was higher (41° C.) than in the other experiments, in which 

 it was 36° C. 



Fig. 2. 



The fact that veins contract under the action of adrenin renders it highly 



probable that veins possess venoconstrictor fibres supplied from the thoracico- 



lumbar sympathetic system. Several observers have concluded that the 



portal veins contain venomotor nerves ; but the presence of such nerves in 



other veins rests mainly on the evidence of Thompson* and Bancroft,! who 



* Thompson, ' Archiv f. Physiol.,' 1893, p. 102. 



t Bancroft, 1 Amer. Journ. Physiol..' 1898, vol. 1, p. 477 



