FUNCTIONS OF THE SWEAT-GLANDS. 283 



Can we conclude that such a system prevails in the sweat- 

 glands? Each glomerule of coiled tubes is surrounded by a 

 plexus of non-medullated fibers containing a number of nerve- 

 cells, while analogy renders it self-evident that the glandular 

 muscles must, as all muscles do, receive their stimulus through 

 nerve-filaments. The fact that they are of the smooth variety 

 does not modify this relationship, since Tschiriew showed that 

 "no essential morphological difference exists between nerve- 

 endings in striated muscles and those in smooth muscles." 

 Dejerine 11 also states that "all nerves end in the form of free 

 arborizations, and the different modes of contraction of the 

 various kinds of muscle in no way depend upon the form of 

 their nerve-terminations/ 7 Finally, Onuf and Collins remark: 

 "For the sweat-glands of the head even Luchsinger admits both 

 a sympathetic (fibers of the cervical sympathetic nerve) and 

 a direct non-sympathetic nerve-supply, the latter being fur- 

 nished either by the spinal cord or the medulla." We have 

 seen that this also applies to the rest of the organism. Ke- 

 duced to its simplest expression, therefore, the functional 

 mechanism of the sweat-glands would be as follows: 



The efferent nerves of the sweat-glands are two in number, 

 loth divisions of the general motor system. One of these, the "in- 

 trinsic vasoconstrictor" is distributed to the glandular arterioles; 

 the other, the "excito-regulator," subdivides into two branches, one 

 of which is distributed to the spiral muscle of the tube and its coils, 

 and the other to the secreting elements. 



When a sweat-gland is active, the "intrinsic vasoconstrictor" 

 nerve constricts the arterioles and thus forces more blood into 

 the glandular capillaries to supply sweat- constituents and work- 

 energy; one subdivision of the "excito-regulator" nerve incites 

 and governs the activity of the secreting elements, while the other 

 causes axial and centripetal contraction of the spiral muscle around 

 the coiled and straight tube. 



The rapidity of the blood-flow through the organ is concur- 

 rently increased through the "extrinsic vasoconstrictor" nerves of 

 the extraglandular arterioles. 



All this being carried on through the agency of a single 

 flow of impulses, the several elements of the process undergo 



u Dejerine: "Anatomic des Centres Nerveux," p. 229, 1895. 



