General Symtomatology and Diagnosis. 5 



seen only in the eyelids or superficial muscles as twitching, and 

 occur in neurasthenia, or in poisoning by strychnia, brucia and 

 other motor nerve poisons. 



Incoordination {Dyskinesis') is the lack of the harmonious 

 balanced movement of the various groups of muscles. Coordina- 

 tion of movement is due to a special mechanism in the spinal cord, 

 and extending forward through the^meduUa oblongata, pons, and 

 crura cerebri to the floor of the third ventricle. In the form of 

 ataxia (lack of power of muscular control) it is usually the result 

 of degeneration (sclerosis) of the superior columns of the cord, 

 of the medulla, pons or crura. It may occur from degeneration 

 or destructive change in the cerebellum, or from disease or sec- 

 tion of the posterior roots of spinal nerves, or finally from the 

 action of certain narcotic poisons (ptomaines, toxins). 



Staggering {titubation) occurs from lesions of the cerebellum, 

 medulla or pons ; also from alcohol, opium, and other narcotics. 



Reflex Action . The normal stimulation of different functions, 

 motor, secretory, circulatory, etc., depends on the nerve centres 

 in the spinal cord, which are roused into action by a centripetal 

 impulse derived from a distant part. Thus the balanced contrac- 

 tion of the different muscles which preserves the equilibrium of 

 the body, depends on the apprehension by the nerve centres, con- 

 sciously or subconsciously, ofsuch contractions (muscular sense), 

 and it is largely under the control of the will. Here three im- 

 pulses act coordinately : ist, the afferent impulse from the mus- 

 cle to the nerve centre ; 2d, the efferent impulse from the nerve 

 centre to the muscle ; and 3d, the inhibitory or controlling, vol- 

 untary impulse from the sensorium to the nerve centre involved. 

 In another case, savory odors, sapid flavors and masticatory move- 

 ments cause a free secretion from the salivary glands. Again, 

 the scratching of a dog's breast causes him to move his hind limb 

 as if he were himself doing the scratching. Again, thepricking 

 of a limb causes the prompt, even if involuntary, contraction of 

 its muscles to withdraw it from the source of irritation. 



Morbid Reflex. Reflex action may be modified in various 

 ways as the result of disease or injury. It may become excessive 

 from irritability of the organ from which the ceotripetal impulse 

 starts, or of the reflex centre in the spinal cord, or of the muscle 

 or other organ to which the centrifugal impulse is directed, or 



