. Nutritional physiology . event in the development of the reflexact occurs. This is localized in the brain or the spinalcord, and we may speak of it as a central process without committing oilrselves as to its exact we actually observe is that the arrival of the afferentimpulses is followed by the appearance of efferent is not necessary to decide whether these efferent im-pulses are the same currents which just entered the in-tricate fabric of the central organ and which have found apath open through its mazes which has led them out REFLEX ACTION 49 again. That is one w
. Nutritional physiology . event in the development of the reflexact occurs. This is localized in the brain or the spinalcord, and we may speak of it as a central process without committing oilrselves as to its exact we actually observe is that the arrival of the afferentimpulses is followed by the appearance of efferent is not necessary to decide whether these efferent im-pulses are the same currents which just entered the in-tricate fabric of the central organ and which have found apath open through its mazes which has led them out REFLEX ACTION 49 again. That is one way of picturing the to the older and more familiar view the impulseswhich come out are not those which went in, but a newset generated by an energetic metaboUc process, a dischargeon the part of cells in the brain or the cord. If this is thetrue conception the afferent impusles serve to touch offirritable nervous elements, much as these elements in theirturn may touch off muscle-fibers or Kg. 6.—^The principle of reflex action. The subject touches a hotobject (H). AlFerent nerve-Impulses travel the route marked bydots and dashes to the spinal cord (S). Efferent impulses returnpromptly along the route marked by little crosses to the muscle (ilf),which co-operates with others not shown to withdraw the fingerfrom the stimulating surface. The situation of the co-ordinatingcenter is left undetermined, whether in the brain or the cord. The fourth step in the evolution of the reflex is theefferent transmission. This may be said always to be morevoluminous than the afferent flow which went go out by many channels, where but few wereengaged in bringing them in. A great characteristic ofthe central process is the spreading of the initial stimu-lation, so that there seems to be no proportion between the 4 50 NUTRITIONAL PHYSIOLOGY cause and the response. The number of nerve-fiberswhich can be excited by the slender proboscis of a mosqui
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Keywords: ., bookcentury1900, bookdecade1910, bookidcu31, booksubjectnutrition
