RHYTHMIC MUSCLES 271 



That nerves influence voluntary and also involuntary muscles is beyond doubt. The voluntary muscles are 

 directly under nerve control. The involuntary rhythmic muscles are hkewise, within limits, amenable to nerve 

 action. Thus in the phenomenon known as blushing, a rude remark or suggestion acting on the cerebro-spinal 

 and vaso-motor nervous system causes the arterioles to open or relax, with the result that the capillary blood- 

 vessels become gorged with blood and produce a temporary redness of the skin. Alarm, or fear, or shock, produces 

 an opposite result, by reducing the size of the arterioles and temporarily depleting the capillaries of blood, which 

 induces paleness of the skin. The movements of the heart can also be quickened and slowed by the division and 

 irritation of certain nerves. Notwithstanding the very intimate relation which exists between involuntary muscles 

 and nerves, it is safe to conclude that the rhythmic muscles can, and do, act either with, or without, nerves. The 

 major portion of the nerves going to the involuntary rhythmic muscles are sympathetic ganglionic nerves, and 

 there is every reason to believe that these are endowed with independent rhythmic powers. The sympathetic 

 ganglionic nerves are primary or fundamental, and take precedence of the cerebro-spinal nerves in the order of 

 development. They carry on the vegetative functions of the body independently of, or in conjunction with, the 

 spinal cord. This they do, even in the absence of a brain, as in the anencephalous foetus. A brain is not necessary 

 to the performance of voluntary movements in certain of the lower animals, as, for example, the medusa and five- 

 rayed star-fish. As I have explained elsewhere,^ the involuntary or rhythmic muscles are to be regarded as the 

 forerunners or parents of the voluntary ones : indeed the movements of even the voluntary muscles are essentially 

 rhythmic in character. Sir James Paget endeavoured to explain that the rhythmic action of muscles was due to 

 rhjdihmic nutrition, but it is difficult to understand how muscles which are, in a sense, continually in action can be 

 fed at stated intervals ; the more especially as the blood or nutritive fluid is constantly circulating through their sub- 

 stance. As the several rhythmic structures referred to are all equally well nourished, it is evident that hypothetical 

 rhythmic nutrition cannot be the real or sole cause of rhythmic movements. In other words, the supply of blood 

 being continuous, it is reasonable to iiifer that the nourishing process is practically continuous, and not interrupted 

 or rhythmic. 



Development and comparative anatomy distinctly point to an inherent rhythmic power in rhythmic structures 

 as apart from nutrition, and even as apart from muscles and nerves and every form of irritabihty and artificial 

 stimulation. This follows because, as explained, the rhythmic structures are being continuously fed ; because the 

 heart opens and closes before it contains blood, muscle, or nerve, and because in plants (in Volvox globator, for 

 example), where neither blood, muscle, nor nerves are present, well-defined rhythmic movements occur. 



While rhythmic movements are to be regarded as spontaneous, inherent, and fundamental endowments on 

 which the Ufe and well-being of the individual depends, it is well to bear in mind that in the higher animals, where 

 muscles and nerves are present, the movements can in part be traced to the muscles, and an intimate relation 

 between the muscles and nerv^es estabUshed. 



In the higher organisms, the muscles and nerves act together, and both display rhythmic movements or im- 

 pulses. It is not possible to distinguish with any degree of precision as between the rhythms in muscles and nerves. 

 As differentiation proceeds, and structure is added to structure, the added structures in every instance conform 

 to a general plan and the carrying out of a common object. In other words, added structures do not wage war with 

 pre-existing structures. On the contrary, all the structures, whether developed late or early, work harmoniously 

 together and to a given end. But for design and preconcerted action a compound organism would be impossible. 

 The rise, progress, and completion of the higher animals all proclaim design and a First Cause. The higher 

 animals are to be regarded as completed wholes, the integral parts of which are essential and necessary. For 

 this, if for no other reason, it is never safe to rely on experiments which have for their object the isolation of parts, 

 organs, and systems. In like manner, the division and irritation of nerve structures, and the artificial stimula- 

 tion of muscles, cannot possibly yield quite normal results. Whatever disturbs the natural balance of an animal 

 inevitably leads to a greater or less degree of abnormal action. Thus the administration of drugs, of chloroform 

 and other anajsthetics, of poisons, &c., tends to abnormal action ; the abnormaUty being greatly increased where 

 coma and nervous shock are produced. 



A violent aperient gives an exaggerated idea of the rhythmic activity of the alimentary canal : an emetic 

 reverses the action of the CESophagus and stomach : strychnine and the injury of certain parts induce tetanus and 

 convulsions : chloroform destroys sensation and renders muscles flaccid : excessive tea drinking produces indigestion 

 and tumultuous action of the heart : excessive stimulation by alcohol results in great general excitement and 

 mental disturbance, and, if long continued, begets coma, collapse, and death. The administration of opium, Indian 

 hemp, &c., leads to a dreamy condition of the brain and nervous system. The greater the liberty taken with an 

 organism the less reliable are the results obtained by experiment. The common practice of irritating, stimulating, 

 1 "The Physiology of the Circulation in Plants, in the Lower Animals, and in Man." (Edinburgh Medical Journal, 1873.) 



