294 THE ADRENAL SYSTEM AND VASOMOTOR FUNCTIONS. 



continued in the next, but the following deductions regarding 

 the several organs the physiology of which has been analyzed 

 appear warranted: 



1. The sympathetic system is structurally a part of the gen- 

 eral cerebro-spinal motor system, and is endowed with no function 

 other than that appertaining to the motor system: i.e., to transmit 

 efferent impulses. 



2. All efferent nerves distributed to the voluntary muscles, to 

 the salivary, mammary, and cutaneous glands, are subdivisions of 

 the general cerebro-spinal motor system. 



3. The general motor nerves distributed to the organs above 

 mentioned divide, when near their destination, into two branches: 



(1) an "extrinsic vasoconstrictor" branch, which supplies filaments 

 to the arteries outside the contractile or secretory structures of the, 

 organ concerned, and increases the speed of the blood-flow through 

 the latter during activity by reducing the caliber of these arteries; 



(2) an "excito-regulator" branch, which supplies the intrinsic 

 structures of the organ and governs their functional activity. 



4. In voluntary muscles and in the salivary, mammary, and 

 cutaneous glands there are two sets of intrinsic arterioles: (1) a 

 set which supplies capillaries to the contractile or secretory ele- 

 ments; (2) a set that does not, but, instead, crosses over to the 

 venules before the contractile or secretory elements are reached. 



5. In the glands mentioned the excito-regulator branch sub- 

 divides into two branches: one of these, the "excitor," supplies 

 filaments to the secretory elements and excites them to activity; 

 the other, the "intrinsic constrictor," is distributed to the intrinsic 

 arterioles that do not supply the secretory structures with capil- 

 laries, constricts them during activity, and thus increases the 

 blood-flow through those that do supply capillaries to the secretory 

 structures. 



6. In muscles the excito-regulator branch also subdivides into 

 two branches: one of these, the "excitor," supplies filaments to the 

 muscle-fibers and excites them to activity; the other, the "intrinsic 

 constrictor," is distributed to the muscular arterioles that do not 

 supply the muscular fibers with capillaries, constricts them during 

 muscular contraction, and thus increases the blood-flow through 

 those that do supply capillaries to the contractile elements. 



7. As all the nervous subdivisions referred to, including the 



