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sions when mingled with other nerves distributed to the same organ, 

 or for tracing its fibres with certainty through the intricacies of a 

 plexus to which various nerves contribute. He has suggested, too, 

 the employment of this method to determine the course and con- 

 nexions of particular tracts of nervous fibres in the brain and spinal 

 cord. 



Dr. Waller has himself applied this method with much success in 

 unravelling the ultimate distribution of the nerves of the tongue, and 

 in investigating the constitution of the cervical part of the sympathetic 

 nerve and its relation to the spinal cord ; and his process has also been 

 successfully employed by others in similar inquiries. 



But the application of Dr. Waller's process is not confined to ana- 

 tomical investigation alone. He has shown how it may serve also to 

 elucidate the functions of nerves. The disorganization of nerve- 

 fibres consequent on their section involves the loss of their functional 

 activity ; and, accordingly, when a nerve contains fibres derived from 

 two or more sources and operates functionally on several different 

 organs, its function may be analysed, as it were, by the separate sec- 

 tion and disorganization of its different tributaries and consequent 

 elimination of the special function of each from the general effect. In 

 this way Dr. Waller has been able to show that the influence of the 

 pneumogastric nerve over the motion of the heart, and in great part 

 also its government of the motions of the larynx, depend on fibres 

 which are contributed to that nerve by the spinal accessory. 



Having once perceived that the changes consequent on the division 

 of nerves might afford a valuable' means of research, Dr. Waller was 

 naturally led to study with care the progress and characteristic 

 features of the disorganizing process, and the modifications of it 

 depending on the nature of the animal subjected to experiment, on 

 age, external temperature, and other circumstances. In the course 

 of these investigations he found that, when the cut ends of a divided 

 nerve are reunited by the healing process, the fibres of the distal 

 or severed part first suffer atrophy throughout their whole length, 

 and are then regenerated, or at least restored to their original inte- 

 grity. 



Another result of this inquiry was the discovery of an important 

 relation between the ganglia of the spinal nerves and the nutrition of 

 their sentient fibres. This fact, previously unknown, but now fully 



