154 PHYSIOLOGY OF MUSCLES AND NERVES. 



everywhere to be found. In the researches in which 

 we are about to engage, we must always endeavour as 

 far as possible to exclude these accidental currents, or 

 at least to distinguish them from those currents which 

 it is our task to examine, and the causes of which lie 

 in the animal tissues themselves. Apart from muscles 

 and nerves, but one tissue seems endowed with some- 

 what strong electric action ; this is that of the glands. 

 This has, indeed, not as yet been fully proved, but it 

 has been shown to be in a very high degree probable. 

 In connection with this it is a very interesting fact that 

 the glands are in some ph3^siological respects very similar 

 to the muscles, and that they bear the same relations 

 to nerves as do muscles. 



2. There is, on the other hand, a tissue in which 

 electric action is exhibited in far greater strength, so 

 that its nature was known long before it was recog- 

 nised that muscles and nerves possess the same capa- 

 city. This tissue does not, however, occur in all 

 animals, but only in a few fishes, which on this account 

 are called electric fishes. In these animals special 

 organs of peculiar structure occur, in which, as in. an 

 electric battery, currents of very considerable strength 

 arise, the discharge of which is caused by the influence 

 of the will, the animal using this power to frighten its 

 enemies, or to benumb and kill its prey. Long before 

 the world knew anything accurately as to the physical 

 nature of electric plienomena, such powerful influences 

 as are exhibited in electric fishes did not fail to attract 

 the attention of chance observers. Notices of these 

 remarkable phenomena are actually found in ancient 

 writers ; and the Roman poet Claudius Claudianus ' 



' Ho lived in Alexandiia toward the end of the fourth century. 



