Decembbe 4, 1914] 



SCIENCE 



803 



1812, and seemingly confirmed by the Webers' 

 discovery that stimulation of the vagus nerve 

 vrill stop the heart (1845) ; and by the discovery 

 of intrinsic nerve ganglia in the heart by 

 Eemak (1848) and Bidder (1852), which were 

 thought to be involved in the celebrated ex- 

 periment of Stannius (1852), viz., that a liga- 

 ture or cut between the sinus venosus and the 

 auricles produces standstill, while a second 

 ligature applied to the aurieulo-ventricular 

 groove causes the ventricle to beat again. The 

 modern revival of the myogenic theory is the 

 work of Engelmann and Gaskell. 



Between 1874 and 1881, Gaskell made a long 

 series of ingenious investigations upon the 

 musculature and innervation of the heart, the 

 results of which, as given in his great memoir 

 of 1881^ and later, may be summarized, how- 

 ever inadequately, as follows : 



1. The motor impulses from the nerve ganglia 

 in the sinus venosus are discrete, not continuous, 

 stimuli, influencing the rhythm of the heart (its 

 rate and force) but not originating either its move- 

 ments or its beat. 



2. Cardiac muscle can contract of itself and is a 

 stimulus-producer. The five properties of cardiac 

 (or other) muscle, as deduced by Gaskell, are ex- 

 citability, conductivity, tonicity, rhythmieity and 

 automatic contractile power. This power of auto- 

 matic, rhythmic contractility has been recently 

 confirmed in Burrows 's extra-vital cultures of em- 

 bryonic heart muscle,^ which contain no nervous 

 tissue whatever. 



3. That the automatic contraction wave proceeds 

 from sinus venosus to ventricle without nervous 

 intervention is proved by Gaskell's and Engel- 

 mann 's sections in the cardiac muscle, excluding 

 the nervous tissues, and leaving only a narrow 

 isthmus for the transmission of the rhythmic im- 

 pulse. Gaskell reversed this peristaltic wave by 

 stimulating the ventricle after the second Stannius 

 ligature, showing that the normal impulse could 

 not have started from the cardiac ganglia. 



4. Gaskell first produced experimental "heart- 

 block" (a term of Ms invention) by clamping the 

 aurieulo-ventricular and sino-auricular grooves, 

 which he calls "the two natural blocking points" 

 of the muscular contraction wave. In his view, 

 the original Stannius experiments become simple 



2 Phil. Tr., Lond., 1883, CLXXIII., 993-1033. 



3 Science, 1912, XXXVI., 90-92. 



cases of temporary block. This view has been 

 brilliantly confirmed by the discovery of the ves- 

 tigial muscular structures known as the aurieulo- 

 ventricular bundle of His and the sino-aurieular 

 node of Keith and Flack; also by the clinical and 

 pathological findings in the disease described by 

 Morgagni in 1761 and now known as heart-block 

 or the Stokes-Adams syndrome. Gaskell even pro- 

 duced the two-, three- and four-time gallops of 

 modern clinicians, in which the ventricle drops one 

 or more of its beats. Sehiff's observation that the 

 ventricle of a dying heart beats slower than the 

 auricle is interpreted as the effect of a gradually 

 increasing block. Gaskell also produced the clin- 

 ical condition known as "fibrillation of the 

 heart " in an isolated strip of cardiac muscle, in- 

 terpreting the phenomenon as due to blocking of 

 the connections between individual muscle cells. 

 In recent medicine, the various rhythmic disorders 

 of the heart are regarded, not as cases of nervous 

 imbalance, but as the effects of blocking of the 

 peristaltic wave which passes from sinus venosus 

 to bulbus arteriosus, and from muscle fiber to 

 muscle fiber. 



5. Schmiedeberg's observation that stimulation 

 of the vagus after administration of nicotine will 

 accelerate the heart led Gaskell to a series of inves- 

 tigations in comparative histology. He found that 

 the hearts of warm-blooded and cold-blooded ani- 

 mals have the same innervation, that the inhibitory 

 fibers of the vagus are medullated, the accelerator 

 fibers non-meduUated, leading to the important 

 conclusion that both sets of fibers belong, not to 

 the cerebro-spinal system, but to "the great sys- 

 tem of efferent ganglionated nerves" (autonomic 

 system), the function of which is the redistribution 

 of impulses along collateral paths by means of 

 fibers passing to and from an especial sympathetic 

 ganglion or synapse. The efferent nerve cells of 

 the inhibitory system lie in the heart itself, those 

 of the accelerator system lie in external sympa- 

 thetic ganglia, the nerve cells in either case being 

 a switch (Foster's synapse) for the transmission 

 of impulses. In 1890, Langley showed that nico- 

 tine wiU paralyze the medullated or pre-ganglionio 

 fiber of a sympathetic ganglion without affect- 

 ing the non-medullated (post-ganglionic) fiber. 

 Schmiedeberg's experiment was, therefore, only a 

 special case of Langley 's nicotine effect. He was 

 really stimulating the preganglionic or inhibitory 

 fibers of the vagus j the switchboard effect across 

 the synapse was abolished, the accelerator fibers 

 from the external ganglia being unaffected by the 

 poison. 



