CONTRACTILITY OF VESSELS. 11- 



The accelerating nerves of the heart, and the position of the 

 nerve-centre from which they spring, were more thoroughly in- 

 vestigated by von Bezold,* while the power of the vagus to 

 weaken as well as slow the heart was observed by Gaskell. The 

 position of the cardiac centre, which, like the rider, regulates 

 the movements of the heart, was located in the medulla 

 oblongata chiefly by Ludwig and his scholars. Like the heart, 

 the vessels are regulated in diameter by the nervous system in 

 accordance with the wants of the body generally ; and the effect 

 upon the vaso-motor nerves which, when cut, allow them to 

 dilate, and, when stimulated, cause them to contract, was dis- 

 covered by Bernard, Brown-Sequard and by our countryman, 

 Waller; while the power of other nerves to cause immediate 

 dilatation was discovered by Bernard, Eckhardt, and Ludwig in 

 the submaxillary glands, penis and peripheral vessels respec- 

 tively.! 



The heart, when cut out of the body, still continues to beat, 

 although removed completely from the influence of the central 

 nervous system, and the vessels have a somewhat similar power 

 of independent contractility. The alterations produced in the 

 circulation, generally and locally, by the contractile power of 

 the A^essels, and the changes caused in the vessels by the central 

 nervous system, by peripheral stimulation of the nerves, or by 

 variations in the quality of the blood, have formed the subject 

 of a series of researches extending over many years ; and 

 though originated, and in many cases entirely conducted by 

 Ludwig, have appeared to a great extent under the names of his 

 pupils. The starting-point of these investigations was an exami- 

 nation of the changes in blood as it flowed through isolated 

 organs, with the view of ascertaining in what manner the com- 

 bustion by which the animal heat is maintained, is effected in 

 the body. While keeping up the circulation of blood through 

 the vessels of muscles severed from the body, Ludwig and 

 Sczelkow+ observed variations in the flow which appeared to 



* Von Eezold, Untersuchungen iiher die Innervation des Herzens, 1863. 

 Leipzig : Engelmanii. 



f Ludwig and Brunton, Ludivig's Arheiten. Vierter Jahrgang, 1869, p. 106. 



X Ludwig and Sczelkow, Renle and Pjeuffers Zeitschrift, 18G3, voL 17, 

 p. 106, and vide p. 122. 



