Physiology. — "The. Presence of Ccvdio-regidntive .Verves in Petro- 

 myzoji fluviatills" . Bj J. B. Zwaardk.maker. (Communicated 

 hy Prof'. H. Zwaahdemakek.) 



(Gominuiiicated at tlie meeting of March 24, 19i!3i. 



Ill llie 2'"' edition of Ids "Plijsioiogie des Kreislaiifs" Tigkrstedt ') 

 remaiks lliat iidiibitory cardiac, nerves are present in nearly all 

 vertebrates. Only among tlie cycloslomata some exceptions are 

 known. Greene') found that in Mvxiiie electrical slimniation, starting 

 from the iirain, I lie spinal cord or the vagi did not atfect the 

 frequency of the heart-beat. Carlson') corrol)orated this finding and 

 tried to extend llie investigation to another group of cjclostomata, 

 viz. (lie petromyzonta. At fust he could work oidy on the larval 

 form, ill which cardio-regnlative nerves appeared to be absent. 

 Afterwards he examined adult animals *). When, in these experiments, 

 he ap[)lied an electrical stimulus to the medulla oblongata on the 

 level of the vagus nucleus, he noted a brief standstill, which was 

 followed by an accelerated rhythm. From this he concludes that 

 "the central nervous system is connected with the heart by ordinary 

 augmentor and probably also by iidiibitory nerves" (I.e. p. 231). 



In the continuing volume of his "Vergleichende Anatomie dei' 

 Myxinoiden" Johannes Müi.i.ek makes mention of a connection 

 between. N. sympathicus and cardiac nerves*). He also adds some 

 remarks about the N. vagus, for which I think it better to refer to 

 the original work (1. c. p. 59 sqq.) 



The first experiments which I made myself to ascertain whether in 

 petromyzon tliiviatilis any influence is exerted by the central 

 nervous system upon the heart's action, yielded a negative 

 result, which was in accordance with Greene and with the first 

 set of experiments performed by Carlson '). However, I have 

 been in a position to extend my research. In order to preclude 



^) R. TiGEHSTEDT, Die Physiologie des Kreislaufs II p. 319. 

 ») Ch. VV. Greene, Amer. Journ. of I'hysiol. VI p. 318 1901. 

 ') A. J. Gaklson, Zeitschr. f. allg. Physiol. IV p. 259 1904. 

 *) A. J. Carlson, Amer. Journ. of Physiol. XVT p. 280 1906. 

 ^) J. Muller, Fortselzung der vergleichenden Anatomie der Myxinoiden p. 57. 

 Berlin 1838. 

 •) J. B. Zwaardemakee, Physiologendag Amsterdam Dec. 1922. 



