LINES OF COMMUNICATION AND FORCE 131 



and of force of the child in utero are twofold, namely, as between the separate parts of the developing fcetus, and as 

 between the foetus as a whole and its parent. 



Perhaps the best example of a rudimentary typical nervous system is that supplied by the five-rayed starfish 

 (Fig. 1, Plate Ivii.). This consists of a commissural ring of nervous matter surrounding the mouth. In this ring, 

 at the base of each ray or hmb, occur nerve gangha, and in connection with them two sets of nerves — namely, a 

 sensory set, extending between the skin or integumentary system to the ganglia, and a motor set, proceeding 

 from the gangUa to the muscular system. There is as yet no trace of a brain. The nervous system of the 

 starfish lays down, unmistakably, the apparatus by which lines of communication are estabhshed, and impulses 

 transmitted. It provides for the transmission of sensory impressions from without and motor impulses from 

 within. The starfish is a sensitive living thing, and can move voluntarily. A brain is not necessary to the more 

 rudimentary and lower forms of voluntary movement. By means of its sensitive nerves the starfish is made aware 

 of matters outside itself. By means of its motor nerves and muscles it can move its body towards anything it 

 fancies. It can also remove its body, or part of it, out of the way of danger. The movements of the starfish are 

 generally spoken of as reflex movements, but they can only be regarded as reflex if the starfish be proved to be an 

 automaton pure and simple, which it cannot possibly be. 



The movements of the starfish are not identical with the so-called reflex movements of a decapitated frog, or 

 those of the higher animals where, from a lesion in the upper part of the spinal cord, the brain is virtually 

 detached from the cord and the nervous system generally. 



The theory of reflex action utterly breaks down when applied to the starfish in the following particulars : 

 (a) it makes no provision for the performance of voluntary movements on the part of the animal ; (b) it assumes 

 that all its tissues are highly irritable and excitable (which is not the case) ; (c) it necessitates the application of 

 artificial stimulation before the animal, or any part of it, can or mil act ; (d) it regards the starfish as an automaton, 

 the movements of which are purely mechanical and involuntary, which they certainly are not. The starfish can 

 feel, but there is no proof that the animal in its normal condition is irritable and excitable, and that it must be 

 jogged into activity by outside stimulation. I direct attention at the earUest opportunity to the theory of reflex 

 action as applied to the starfish, because its supporters seek to obscure what they cannot explain, and to set up an 

 artificial boundary as between animals with nerve centres or gangUa plus sensory and motor nerves on the one hand, 

 and animals with all these plus a brain on the other. No such distinction can be drawn. The theory would 

 destroy the conmion ground (whatever its nature) which exists between the lower animals and the highest plants, and 

 between the lower and higher animals themselves. I discuss this subject at considerable length further on when 

 deahng with reflex action, instinct, and reason ; but I desire to warn the reader against rashly accepting a theory 

 which conveys an entirely erroneous impression of the nervous system as a whole. 



Dr. John C. Dalton, the distinguished professor of physiology to the College of Physicians and Surgeons, New 

 York, gives expression to the prevailing behef in these words : " When any stimulus or irritation is apphed to the 

 integument of one of the arms (of the starfish), it is transmitted by the nerves of the integument to the ganghon 

 situated near the mouth. Arrived here, it is received by the grey matter of the gangUon, and immediately converted 

 into an impulse, which is sent out by other filaments to the muscles of the corresponding limb ; and a muscular 

 contraction and movement consequently take place. The muscles therefore contract in consequence of an irritation 

 which has been apphed to the sldn. It must be recollected that this action does not necessarily indicate any sensa- 

 tion or vohtion, nor even any consciousness on the part of the animal. The function of the grey matter is 

 simply to receive the impulse conveyed to it, and to reflect or send back another ; and this may be accomphshed 

 altogether involuntarily, and without the existence of any conscious perception. It is the simplest form of refiex 

 action. Where the irritation apphed to the integument is of an ordinary character and not very intense, it is simply 

 reflected, as above described, from the corresponding ganghon back to the same hmb. But if it be of a pecuUar 

 character, or of a greater intensity than usual, it may be also transmitted by the commissures to the neighbouring 

 gangha ; and so two, three, four, or even all five of the limbs may be set in motion by a stimulus apphed to the 

 integument of one of them. According to the character and intensity, therefore, of the original stimulus, it will 

 be followed by a response from one, several, or all of the different parts of the animal frame." 



In speaking of the nervous system of the centipede he says, " It consists of a linear series of nearly equal and 

 similar gangha arranged in pairs, situated upon the median hne, along the ventral surface of the ahmentary canal. 

 Each pair of gangUa is connected with the integument and muscles of its own articulation by sensitive and motor 

 filaments ; and with those which precede and follow by a double cord of longitudinal commissural fibres. In the 

 first articulation, moreover, or the head, the gangha are larger than elsewhere, and send nerves to the antennae 

 and to the organs of special sense. This pair is termed the cerebral ganghon, or the ' bram.' 



" A reflex action may take place, in these animals, through either one or all of the gangha composing the nervous 



