THE SYMPATHETIC XERVE. 451 



measure from the pneumogastric nerves, yet probably derive 

 through them few filaments except such as have arisen from 

 their ganglia, and are therefore of the nature of sympathetic 

 fibres. 



The parts which are supplied with motor power by the sym- 

 pathetic nerve continue to move, though more feebly than be- 

 fore, when they are separated from their natural connections 

 with the rest of the sympathetic system, and wholly removed 

 from the body. Thus, the heart, after it is taken from the 

 body, continues to beat in Mammalia for one or two minutes, 

 in reptiles and Amphibia for hours ; and the peristaltic motions 

 of the intestine continue under the same circumstances. Hence 

 the motion of the parts supplied with nerves from the sympa- 

 thetic are shown to be, in a measure, independent of the brain 

 and spinal cord. 



It seems to be a general rule, at least in animals that have 

 both cerebro-spinal and sympathetic nerves much developed, 

 that the involuntary movements excited by stimuli conveyed 

 through ganglia are orderly and like natural movements, while 

 those excited through nerves without ganglia are convulsive 

 and disorderly ; and the probability is that, in the natural 

 state, it is through the same ganglia that natural stimuli, im- 

 pressing centripetal nerves, are reflected through centrifugal 

 nerves to the involuntary muscles. As the muscles of respira- 

 tion are maintained in uniform rhythmic action chiefly by the 

 reflecting and combining power of the medulla oblongata, so, 

 probably, are those of the heart, stomach, and intestines, by 

 their several ganglia. And as with the ganglia of the sympa- 

 thetic and their nerves, so with the medulla oblongata and its 

 nerves distributed to respiratory muscles, if these nerves or 

 the medulla oblougata itself be directly stimulated, the move- 

 ments that follow are convulsive and disorderly ; but if the 

 medulla be stimulated through a centripetal nerve, as when 

 cold is applied to the skin, then the impressions are reflected 

 so as to produce movements which, though they may be very 

 quick and almost convulsive, are yet combined in the plan of 

 the proper respiratory acts. 



Among the ganglia of the sympathetic nerves to which this 

 co-ordination of movements is to be ascribed, must be reckoned, 

 not those alone which are on the principal trunks and branches 

 of the sympathetic external to any organ, but those also which 

 lie in the very substance of the organs ; such as those dis- 

 covered in the heart by Remak. Those also may be included 

 which have been found in the mesentery close by the intestines, 

 as well as in the submucous tissue of the stomach and intestinal 

 canal (Meissner), and in other parts. The extension of dis- 



