VASOMOTOR SUPPLY OF THE ORGANS. 563 



best known of the sacral autonomic system. They enter the ner- 

 vus erigens and thence reach the organs by way of the pelvic 

 plexus. The especial importance of these fibers in the process of 

 erection is described in the section on the physiology of the repro- 

 ductive organs. The internal -genital organs uterus, vagina, 

 vas deferens, seminal vesicles, etc. receive no vasomotor fibers 

 from the sacral autonomic system, that is, from the nervi erigentes 

 but do receive a supply of constrictor fibers from the sympathetic 

 system. These latter fibers emerge from the cord in the roots of 

 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 shown or claimed (p. 

 548) that the dilator effect in the limbs is due to the antidromic 

 action of sensory 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 uncertain 

 whether this result is brought about solely, by an increased activity 

 of the heart or by the combined effect of vasodilatation and in- 

 crease in heart- work. Kaufmann { 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 



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

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



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



j Kaufmann, " Archives de physiologic normale et pathologique, " 1892, 

 pp. 279 and 495. 



