i oo THE INVOL UNTAR Y NER VO US S YSTEM 



fibres from the central nervous system. To this intrinsic nervous 

 system all normal rhythmic action in these muscles is supposed 

 to be due, and through the medium of its afferent and efferent 

 nerve fibres co-ordinated movements are carried on, whether in 

 the form of such peristaltic movements as those of the intestine 

 or an orderly sequence of contractions as in the case of the heart. 

 It is maintained that this intrinsic nervous system is composed of 

 a network of fibres, with inclusive nerve cells situated within the 

 organs themselves ; and is therefore exclusive of the groups of 

 nerve cells which lie outside the organs and can be removed 

 without prevention of rhythmic or peristaltic action. 



I will first take the question of rhythmical and peristaltic 

 movements as shown in the case of the heart, and consider the 

 evidence of the part played by the nerve cells in the heart itself. 



Three possibilities suggest themselves : 



1. The nerve cells in the heart discharge rhythmically, and 

 the heart muscle behaves in a manner similar to voluntary muscle 

 and has no special rhythmic power. 



2. The rhythmic power is in the cardiac muscle, and the 

 nerve cells assist in the maintenance of that rhythmic power 

 by maintaining the muscle in that fit condition of instability 

 which results in rhythmic contractions. 



3. The nerve cells within the heart have no more to do with 

 the rhymthic power of the heart than the nerve cells outside 

 the heart. In both cases they and their nerve fibres are regula- 

 tors not initiators of rhythm ; the rhythmic power is in the 

 muscles themselves. 



The history of the investigations upon the origin of the rhythm 

 of the heart shows that, with the discovery of the ganglion cells 

 in the sinus of the heart (Remak's ganglia), the rhythmic beat 

 was naturally attributed to the action of those ganglion cells ; and 

 the conception arose that these cells were motor cells, which dis- 

 charged rhythmically and sent separate impulses to the muscular 

 tissue of the heart, thus causing separate contractions and bring- 

 ing about the rhythmic beat. The due sequence of the contrac- 

 tions of the different chambers of the heart was brought about by 

 a nervous mechanism, presumably ganglionic in nature, interposed 

 between the main motor centres in the sinus (Remak's ganglia) 

 and the auricular and ventricular muscle masses respectively. 

 Nerve cells with such presumed nervous function were found by 



