Apkil 1, 18fi7.] 



HARDWICKE'S SCIENCE-GOSSIP. 



77 



organisms lias not come under consideration. 

 Morphology and distribution might be studied 

 almost as well, if animals and plants were a 

 peculiar kind of crystals, and possessed none of 

 those functions which distinguish living beings so 

 remarkably. But the facts of morphology and dis- 

 tribution have to be accounted for, and the science, 

 whose aim it is to account for them, is physiology. 



Let us return to our lobster once more. If we 

 watched the creature in its native element, we 

 should see it climbing actively the submerged rocks, 

 among which it delights to live, by means of its 

 strong legs ; or swimming by powerful strokes of 

 its great tail, the appendages of whose sixth joint 

 are spread out into a broad fan-like propeller ; seize 

 it and it will show you that its great claws are no 

 mean weapons of offence ; suspend a piece of carrion 

 among its haunts, and it will greedily devour it, 

 tearing and crushing the flesh by means of its 

 multitudinous jaws. 



Suppose that we had known nothing of the lobster 

 but as an inert mass, an organic crystal, if I may 

 use the phrase, and that we could suddenly see it 

 exerting all these powers, what wonderful new ideas 

 and new questions would arise in our minds ! The 

 great new question would i be, "How does all this 

 take place ? " the chief new idea would be the idea 

 of adaptation to purpose, — the notion that the con- 

 stituents of animal bodies are not mere unconnected 

 parts, but organs working together to an end. Let 

 us consider the tail of the lobster again from 

 this point of view. Morphology has taught us that 

 it is a series of segments composed of homologous 

 parts, which undergo various modifications — beneath 

 and through which a common plan of formation is 

 discernible. But if I look at the same part physio- 

 logically, I see that it is a most beautifully con- 

 structed organ of locomotion, by means of which 

 the animal can swiftly propel itself either backwards 

 or forwards. 



But how is this remarkable propulsive machine 

 made to perform its functions ? If I were suddenly 

 to kill one of these animals and to take out all the 

 soft parts, I should find the shell to be perfectly 

 inert, to have no more power of moving itself than 

 is possessed by the machinery of a mill, when dis- 

 connected from its steam-engine or water-wheel. 

 But if I were to open it, and take out the viscera 

 only, leaving the white flesh, I should perceive that 

 the lobster could bend and extend its tail as well as 

 before. If I were to cut off the tail I should cease 

 to find any spontaneous motion in it — but on pinch- 

 ing any portion of the flesh, I should observe that 

 it underwent a very curious change— each fibre be- 

 coming shorter and thicker. By this act of contrac- 

 tion, as it is termed, the parts which the ends of the 

 fibre are attached are, of course, approximated ; 

 and according to the relations of their points of 

 attachment to the centres of motion of the different 



rings, the bending or the extension of the tail results. 

 Close observation of the newly-opened lobster would 

 soon show that all its movements are due to the 

 same cause — the shortening and thickening of these 

 fleshy fibres, which are technically called muscles. 



Here, then, is a capital fact. The movements of 

 the lobster are due to muscular contractility. But 

 why does a muscle contract at one time and not at 

 another? Why does one whole group of muscles 

 contract when the lobster wishes to extend its tail, 

 and another group, when he desired to bend it ? 

 What is it originates, directs, and controls the 

 motive power ? 



Experiment, the great instrument for the ascer- 

 tainment of truth in physical science, answers this 

 question for us. In the head of the lobster there 

 lies a small mass of that peculiar tissue which is 

 known as nervous substance. Cords of similar 

 matter connects this brain of the lobster, directly or 

 indirectly, with the muscles. Now, if these com- 

 municating cords are cut, the brain remaining entire, 

 the power of exerting what we call voluntary motion 

 in the parts below the section is destroyed, and on 

 the other hand, if, the cords remaining entire, the 

 brain mass be destroyed, the same voluntary mobility 

 is equally lost. Whence the inevitable conclusion 

 is, that the power of originating these motions 

 resides in the brain, and is propagated along the 

 nervous cords. 



In the higher animals the phenomena which attend 

 this transmission have been investigated, and the 

 exertion of the peculiar energy which resides in the 

 nerves, has been found to be accompanied by a dis- 

 turbance of the electrical state of their molecules. 



If we could exactly estimate the signification of 

 this disturbance ; if we could obtain the value of a 

 given exertion of nerve force by determining the 

 quantity of electricity or of heat of which it is the 

 equivalent ; if we could ascertain upon what arrange- 

 ment, or other condition of the molecules of matter, 

 the manifestation of the nervous and muscular 

 energies depends (and doubtless science will some 

 day or other ascertain these points), physiologists 

 would have attained their ultimate goal in this direc- 

 tion ; they would have determined the relation of 

 the motive force of animals to the other forms of 

 force found in nature ; and if the same process had 

 been successfully performed for all the operations 

 which are carried on, in and by, the animal frame, 

 physiology would be perfect, and the facts of morpho- 

 logy and distribution would be deducible from the 

 laws which physiologists had established, combined 

 with those determining the condition of the sur- 

 rounding universe. 



There is not a fragment of the organism of this 

 humble animal, whose study would not lead us into 

 regions of thought as large as those which I have 

 briefly opened up ; but what I have done, I trust, 

 has not only enabled my readers to form a conception 



