DISORDERLY REFLEX MOVEMENTS. 577 



of the body to contract, and the animal is convulsed. Here 

 then we see that a feeble stimulation causes a limited and 

 purpose-like response; stronger causes a wider radiation of 

 efferent impulses from the cord and the con traction of more 

 muscles, but still the movements are co-ordinated to an 

 end; while abnormally powerful stimulation of the sensory 

 nerves throws all the motor fibres arising from the cord into 

 activity, and calls forth inco-ordinate spasmodic action. 

 The orderly movements are very uniform for a given stimu- 

 lation; if the anal region be pinched, both hind legs are 

 raised to push away the forceps; if a tiny bit of bibulous 

 paper moistened with dilute vinegar be put on the thigh, 

 the lower part of that leg is raised to wipe it oil; if on the 

 middle of the back near the head, both feet are wiped over 

 the spot; if on one flank, the leg and foot of that side are 

 used, and so on; in fact, by careful working, the frog's skin 

 can be mapped into many regions, the application of acidu- 

 Lited water to each causing one particular movement, 

 due to the co-ordinated contractions of muscles in different 

 combinations, and never, under ordinary circumstances, 

 any but that one movement. The above purpose-like 

 Teflex movements may all be characterized as defensive. 

 but all orderly reflexes are not so. For example, in the 

 breeding season the male frog clasps the female for several 

 days with his fore limbs. If a male at this season be 

 decapitated and left to recover from the shock, it will be 

 found that gently rubbing his sternal region with the finger 

 causes him to clasp it vigorously. 



Disorderly Reflexes or Reflex Convulsions. These 

 come on when an afferent nerve-trunk is stimulated instead 

 of the tactile end organs in the skin; or when the skin is 

 very powerfully excited; or, with feeble stimuli, in certain 

 diseased states (pathological '_. tetanus}, and under the in- 

 fluence of certain poisons, e^ecially strychnine. If a frog 

 or a warm-blooded animal be given a dose ot the latter drug, 

 a stimulus, such as normally would excite only limited 

 orderly reflexes, will excite the whole cord, and lead to 

 discharges along all the efferent fibres so that general con- 

 vulsions result. It has been clearly proved that, in such 



