52 NUTRITIONAL PHYSIOLOGY 



frog adroitly catches a fly it is natural to assume a desire 

 and a design on the part of the frog. Scientific analysis 

 nevertheless makes it appear far more probable that the 

 fly is entrapped because the frog is a mechanical device 

 adapted to do this thing over and over again. The eye 

 receives the flitting shadow of the insect, the stimulus 

 excites the brain, and the well-directed fling of the tongue 

 follows. The reflex is not done away with when the part 

 of the brain most likely to stand in relation to consciousness 

 has been destroyed. We have to remember that much of 

 the service of the eye is subconscious, as when it makes us 

 turn aside from obstacles in our path. It is in this way 

 that the eyes of the somnambulist assist in guiding his 

 movements. Conscious attention is no more essential to 

 such a use of the eyes in the waking than in the abnormal 

 sleeping state. In fact, close attention to the balancing 

 of the body is quite as likely to derange as to promote the 

 reflex adjustment. 



Central Resistance. Reflexes are not obtainable with 

 the same ease at all times. We express this fact by saying 

 that there are variations of resistance in the central ner- 

 vous system. If reflexes are hard to bring about, we say 

 that the resistance is high ; if they occur with unusual free- 

 dom and seem disproportionate to the exciting stimuli, we 

 say that the resistance is low. Narcotics and anesthetics 

 are said to raise the resistance, and their effect can be 

 gaged by observing the degree of difficulty with which 

 certain reflexes can be produced, or whether, indeed, they 

 can be produced at all. Drugs of an opposite order, the 

 true stimulants, make it easy to call out most reflexes. 

 When one is distinctly under the influence of coffee, a noise 

 may cause one to start, with a sharp contraction of many 

 muscles. The auditory stimulus has an undue effect, and 

 it is natural to assume that the conditions in the brain and 

 cord are uncommonly favorable to the penetration and to 

 the multiplication of nervous impulses. In poisoning by 

 strychnin such an extension of conduction may exist that 

 some trifling cause may precipitate a terrific and exhaust- 



