362 DISEASES OF THE PERIPHERAL NERVES. 



by its sensory fibres, is an important criterion of the peripheral origin 

 of the disease. 



4. The absence of reflex and sympathetic movements in the region 

 of the palsied nerve is of similar import. If the continuance of the 

 normal sensibility informs us that the function of the sensory nerves 

 of a part is still preserved, and that its connection with the brain re- 

 mains intact ; and if, nevertheless, no reflex signs arise when the sen- 

 sory nerves are irritated, there can remain no doubt that an interrup- 

 tion exists in the motor nerves, and hence that the palsy is peripheral. 

 For instance, if a patient be unable to close his eye at will, and do 

 not even wink when the bulb is touched, although the sensibility of 

 the conjunctiva be normal, the palsy is certainly peripheral. The re- 

 verse of this condition is a still better proof of the central origin of a 

 palsy. If a patient be unable voluntarily to bring a certain nerve into 

 excitement, and, hence, unable to contract the muscles supplied by 

 that nerve (for instance, if he cannot close the eye when told to do so ; 

 and, on the other hand, if the nerve be excited, and all its muscles 

 made to contract if a sensory nerve be irritated, as when we touch the 

 conjunctiva with the finger), we have to do with a central palsy. In 

 such a case the irritability of the motor and sensory fibres is perfect, 

 as is also the path by which the impression is conveyed from the cen- 

 tripetal to the centrifugal nerves ; but the centre of volition in the 

 brain, or the channel through which the influence of the will is im- 

 parted to motor nerves, is destroyed. 



5. Finally, the early extinction of electric contractility in a nerve 

 that is, the absence of contractility of its muscles upon application 

 Df the induced current is an important sign that the paralysis is of 

 oeripheral origin. The induction apparatus, the exaggerated and in- 

 liscriminate employment of which, for therapeutic purposes, should be 

 liscouraged, deserves a much greater employment as a means of diag- 

 nosis, especially in private practice, than it has obtained hitherto. 



In recent cases of peripheral palsy, which come under our notice 

 tolerably often in private practice, and where, owing to the greater 

 prospect of successful treatment, it is of peculiar importance to knpw 

 whether the disease be of peripheral or central origin, examination 

 with the induced current will decide the matter almost with certainty. 

 In many cases of peripheral palsy, the electric contractility of the mus- 

 cles suiks to a minimum, even within a few days after the occurrence 

 of the palsy, and soon afterward ceases entirely. In cerebral paralysis 

 it is quite otherwise. There the electric contractility often continues 

 unimpaired for months. Hemiplegic patients, indeed, are apt to be 

 much impressed when the faradizer, by application of the electrodes, 

 readily causes contraction of muscles, which for months have been be- 



