MUSCULAR ELEMENTS. 14.7 



into them. This is an extremely important feature, in- 

 asmuch as the contraction of these ligaments, in which 

 muscular tissue is not generally considered to exist, is 

 by no means solely to be ascribed to the blood-vessels, 

 as James Traer only a short time ago endeavoured to 

 establish ; on the contrary, we find thickish, flat bundles 

 of muscle which run through the middle of the liga- 

 ments, and during menstrual excitement enable contrac- 

 tions to take place, similar to those which we can follow 

 with such great distinctness in external portions of the 

 genital passages. 



If now the question be raised how far the individual 

 elements of the vessels are of importance in the body, it 

 is at once evident that the contractile elements play the 

 most important part in the coarser processes of the cir- 

 culation, whilst the elastic constituents come next, and 

 the simply permeable, homogeneous membranes last. 

 Let us first consider the import of the muscular elements, 

 and more particularly in those vessels which are chiefly 

 provided with them, namely the arteries. 



When an artery is acted upon by any influence which 

 causes a contraction of its muscular tissue, it must of 

 course become narrower, inasmuch as the contractile 

 cells lie in rings around the vessel ; this contraction may 

 under certain circumstances proceed until the canal is 

 almost entirely obliterated, and the natural consequence 

 then is that less blood penetrates into the corresponding 

 part of the body. When, therefore, an artery is in any 

 way exposed to a pathological irritant, or when it is 

 excited by some physiological stimulus, its proper action 

 cannot be displayed in any other way than by its becom- 

 ing narrower. Now, indeed, that the muscular elements 

 of the walls of the vessels have become known, the old 

 doctrine might again be taken up, that, namely, the vessels, 



