TRANSFERENCE OF IMPRESSIONS. 487 



cognizance of, or exercises influence on, the processes 

 carried on in any part supplied with sympathetic nerves, 

 there must be a conduction of impressions through all the 

 nervous centres between the brain and that part. It is 

 probable that in this conduction through nervous centres 

 the impression is not propagated through uninterrupted 

 nerve-fibres, but is conveyed through successive nerve- 

 vesicles and connecting nerve-filaments ; and in some 

 instances, and when the stimulus is exceedingly powerful, 

 the conduction may be effected as quickly as through* con- 

 tinuous nerve-fibres. 



But instead of, or as well as, being conducted, impres- 

 sions made on nervous centres may be communicated from 

 the fibres that brought them, to others ; and in this com- 

 munication may be either transferred, diffused, or reflected. 



The transference of impressions may be illustrated by the 

 pain in the knee, which is a common sign of disease of the 

 hip. In this case the impression made by the disease on the 

 nerves of the hip-joint is conveyed to the spinal cord; 

 there it is transferred to the central ends or connections of 

 the nerve-fibres distributed about the knee. Through these 

 the transferred impression is conducted to the brain, and 

 the mind, referring the sensation to the part from which it 

 usually through these fibres receives impressions, feels as 

 if the disease and the source of pain were in the knee. At 

 the same time that it is transferred, the primary impression 

 may be also conducted ; and in this case the pain is felt 

 in both the hip and the knee. So, not unfrequently, if 

 one touches a small pimple, that may be seated in the 

 trunk, a pain will be felt in as small a spot on the arm, or 

 some other part of the trunk. And so, in whatever part of 

 the respiratory organs an irritation may be seated, the 

 impression it produces is transferred to the nerves of the 

 larynx ; and then the mind perceives the peculiar sensation 

 of tickling in the glottis, which best, or almost alone, excites 

 the act of coughing. Or, again, when the sun's light falls 

 strongly on the eye, a tickling may be felt in the nose, 



