VASOMOTOR SUPPLY OF THE ORGANS. 629 



the upper lumbar nerves and reach the organs by way of the in- 

 ferior mesenteric ganglion and hypogastric nerve.* 



Vasomotor Supply of the Skeletal Muscles. — Gaskellf es- 

 pecially has given evidence of the existence of vasomotor fibers in 

 the muscles. He concludes, as the result of his work, that the blood- 

 vessels of the muscles receive both vasoconstrictor and vasodilator 

 fibers, but that the latter greatly predominate, — at least, their 

 physiological effect is much more evident in experimental work. 

 As proof of the presence of dilator fibers he gives such results as 

 these: The mylohyoid muscle of the frog is thin enough to be 

 observed directly under the microscope. When curarized and 

 stimulated through its motor nerve the small vessels may be seen 

 to dilate and there is an augmented flow of blood. In a dog section 

 of the motor nerve to a muscle is followed by a greatly increased 

 flow of blood, which, however, is only temporary and is referable to 

 a mechanical stimulation of the dilator fibers. Direct stimulation 

 of the severed nerve causes an increased flow of blood through the 

 muscles, but if the muscles are first completely curarized stimulation 

 causes, on the contrary, a decreased flow. This last result is ex- 

 plained on the supposition that curare paralyzes the endings of the 

 dilator fibers and thus allows the effects of the constrictors to mani- 

 fest themselves. Since, however, Bayliss has given evidence to 

 show (p. 610) that the dilator effect in the limbs is due to the anti- 

 dromic action of afferent fibers, it is evident that this important 

 question needs reinvestigation. Various physiologists have shown 

 that muscular activity is accompanied by an increase in the blood- 

 flow through the muscle, as we should expect, but it remains uncer- 

 tain whether this result is brought about solely by an increased 

 activity of the heart or by the combined effect of vasodilatation and 

 increase in heart-work. Kaufmann J takes this latter view in con- 

 sequence of some interesting results obtained upon horses. He 

 measured the blood-flow through the masseter muscle and the 

 elevator of the lip in a horse in which the muscles were exercised 

 normally by the act of eating. The blood-flow was increased as 

 much as flve times over that observed during rest, and that this 

 increase was due in part at least to a local dilatation seems to be 

 proved by the fact that the blood-pressure in the artery supplying 

 the muscle fell, while that in the vein rose. While, therefore, our 

 experimental knowledge of the vasomotors of the muscles needs 

 further investigation, we may provisionally accept the view ad- 

 vocated by Gaskell, — namely, that the vasomotor supply to the 



* For the bibliography of the vasomotor supply to the various organs see 

 Langley, "Ergebnisse der Physiologie," vol. ii., part ii., p. 820, 1903. 



t Gaskell, "Journal of Physiology," 1, 262, 1878-79. 



t Kaufmann, "Archives de physiologie normale et pathologique," _1892, 

 pp. 279 and 495. 



