Sensory Disturbances. 431 



stantly occurs with palsy of the sphincter and detrusor muscles ; 

 when the detrusor alone is paralyzed and the sphincter is intact the 

 urine collects in the bladder. Paralyses due to destruction of 

 ganglion cells are irreparable; but peripheral palsies may some- 

 times recover by regeneration of nerve fibres. When regenera- 

 tion of nerves does not occur in the spinal palsies due to destruc- 

 tion of the gray matter and anterior nerve roots, the paralyzed 

 muscles undergo atrophy and degeneration, with rapid loss of 

 electrical irritability. Tn case of central palsies atrophy does 

 not occur (Samuel). * 



Sensory Disturbances. — The sensory nerves transmit pres- 

 sure and temperature sensations, special sensations (smell, 

 taste, sight, hearing), and the so-called general sensations 

 (hunger, thirst, special cutaneous sensations, sense of position). 

 It is assumed that just as for the special senses there are par- 

 ticular nerves, there are also for every other sort of sensation 

 special nerves; and it is knov/n that nerves sensitive to pres- 

 sure, pain, cold and heat have entirely specialized and character- 

 istic endings (v. Frey, Krehl). From these local receptive end- 

 organs the sensation is conveyed ccntripetally to the perceptive 

 psycho-sensory parts of the brain, where proper distribution is 

 made to the tracts and innumerable connections occur with the 

 reflex and automatic nerves and ganglia. Disturbances of sensation 

 may be considered as of two types, pathological excitation and 

 pathological depression of sensation. Pathological excitation of 

 sensory nerves gives rise to symptoms of sensory irritation of 

 the most varied forms and grades, according to the kind and 

 position of the terminal organ and the lesions. Sensation of 

 pain is caused by stimulation of the nerves of pain, which are 

 distributed in profusion and have their terminations in the skin, 

 at the mucous membrane orifices, serous and synovial mem- 

 branes; these peripheral parts of the body therefore being capable 

 of manifesting the most severe attacks , of pain. Mechanical, 

 chemical and thermic stimuli induce this symptom. If the 

 nerve be in a condition of exaggerated irritability (hyperces- 

 thesia) ordinary physiological variations (muscular action, ten- 

 sion of tissue, congestion) are sufficient to bring on pain. Cer- 

 tain forms of pain apparently develop spontaneously (nenralgia), 

 that is, without demonstrable anatomical lesions and from unknown 

 changes. The tracts extending from the muscles, bones and 

 glands and into the central nervous system are less sensitive to 

 pain; although painful symptoms may be noticed arising from 



