The laws and mechanics of circulation, with the principle involved in animal movement . ues (Fig. 216), which isnot by inosculation, as Sir Charles Bell thought (the finerwork attained by means of the microscope since then mak-ing this known), but the fibres overlapping simply, whichhas the effect of completely separating the currents, enablingthe outgoing current to pass up the sensory nerves andthe in-going down the other or motor nerves, without in-terference, passing readily in and out of the open end ofthe nerves through the terminal plates for collecting it. Andit must not be supposed fo
The laws and mechanics of circulation, with the principle involved in animal movement . ues (Fig. 216), which isnot by inosculation, as Sir Charles Bell thought (the finerwork attained by means of the microscope since then mak-ing this known), but the fibres overlapping simply, whichhas the effect of completely separating the currents, enablingthe outgoing current to pass up the sensory nerves andthe in-going down the other or motor nerves, without in-terference, passing readily in and out of the open end ofthe nerves through the terminal plates for collecting it. Andit must not be supposed for an instant that the brain gene-rates the nervous force expended in the organism, thoughundoubtedly it contributes greatly to it; but as in the case ofthe spinal centres, its principal role is the separator and 508 GENESIS OF NEEVOIS FOKCE. regulator of the nervous supply, and a> a great reservoir, giv-ing it out in the measure of the requirements. .But if con-stantly drawn upon for producing the voluntary actions, as, forexample, in walking over uneven ground, where every move-. Fig. 216.—Nerves of the Face, fifth and seventh pairs.—Sir Charles Bell. A, facialnerve : B, trunk of same, dissected off and pinned out; C, branch of third division offifth nerve joining the plexus of the facial ; D, masseteric branch of fifth nerve ; E,bucco-labial branch of fifth ; F, branch of fifth to muscles of lower jaw ; G, infra-orbital nerve ; H, mental nerve ; /, infra-trochlear nerve. ment is voluntary, or made directly from the brain, it speedilyinduces exhaustion, though the amount of work actually per-formed falls far short of that done upon even ground, wherethe movements are simply reflex, the brain itself but slightly GENESIS OF NERVOUS FORCE. 509 involved. In fine, the generation of force involves the evolu-tion of heat; hence we must conclude that the main source offorce in the organism must be in the muscles ; nor is it reason-able that the furnace should be in the brain, s
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