The principles of psychology . with each further development of the nervous system,enabling it to make all parts of the body work togethermore efficiently in simultaneous and successive actions,there goes an increased power of evolving the energy re-quired for such larger aggregates of actions. These principles we found to be well exemplified in thecase which most nearly concerns us. It is needless toIe-state the results so recently arrived at. One remark,however, may be added. In the functions of the suc-cessively-higher vertebrate centres, reaching their climaxin the human being, we see well
The principles of psychology . with each further development of the nervous system,enabling it to make all parts of the body work togethermore efficiently in simultaneous and successive actions,there goes an increased power of evolving the energy re-quired for such larger aggregates of actions. These principles we found to be well exemplified in thecase which most nearly concerns us. It is needless toIe-state the results so recently arrived at. One remark,however, may be added. In the functions of the suc-cessively-higher vertebrate centres, reaching their climaxin the human being, we see well exemplified the law ofdevelopment of functions in general (First Princii^les,Part II. § 142). This progress from co-ordinations thatare small and simple to those that are larger and compound,and to those that are still larger and doubly compound, isone of the best instances of that progressive integration ofmotions, simultaneously becoming more heterogeneous andmore definite, which characterizes Evolution under all CHAPTER lY. THE CONDITIONS ESSENTIAL TO NERVOrS ACTION. § 25. Of tliese^ the first in order is continuity of nerve-substance. Disturbance is not conveyed from end to end ofa nerve tliat lias been cut in two; and section of a nerve-centre similarly prevents tlie transfer of an impulse from oneof tbe dissevered parts to tlie otlier. The requisite continuity is not simply the continuity ofunbroken contact: there must be continuity of molecularcohesion. Placing in apposition the two ends of a dividednerve^ does not re-establish nervous communication. Evenwhen, after a cut, the surrounding flesh has been healed, itis long before the sundered nerve-threads re-unite so com-pletely that they transmit stimuli as well as before. Further, there must be no destruction of continuity bymolecular disorganization. Without division of a nerve, andwithout injury of its sheath, there may result from disease achange which incapacitates the nerve-fibres—an atrophy, ora br
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Keywords: ., bookcentury1800, bookdecade1860, bookidpri, booksubjectpsychology
