98 THE ELEMENTARY NERVOUS SYSTEM 



termined. At 21 degrees centigrade this proved to be 

 from 121 millimeters to 146 millimeters a second, a rela- 

 tively slow rate. In the particular form of preparation 

 on which this determination was made, the tissue of the 

 tongue exhibited no contraction during transmission, 

 hence it is to be concluded that the type of transmission 

 here measured was strictly nervous, and not muscular or 

 a combination of nervous and muscular transmission. 



The type of stimulation and response that has been 

 described in the last few paragraphs for the sea-anemone 

 is one of the most extensive and vigorous that this animal 

 can carry out. If the stimulation is sharp and prolonged 

 not only do the longitudinal mesenteric muscles continue 

 to contract, but the tentacles shorten and contract, the 

 circular muscle of the column aids in diminishing the 

 volume of the animal, and, as the water from its interior 

 is discharged, the sphincter, like a puckering string, 

 draws the column over the retreating oral disc till the 

 whole animal is changed from a beautifully expanded 

 flower-like form to a shrivelled, contracted, and almost 

 amorphous mass. In this extreme condition probably all 

 the thirteen or more sets of muscles in the actinian's body 

 have passed into a state of extreme contraction, which 

 justifies more or less the older conception of the sea- 

 anemone as a simple muscular sac. This state of con- 

 traction, a condition of extreme muscle tonus, may en- 

 dure for hours or even days and illustrates well the chief 

 characteristic of the musculature of many of these sim- 

 ple animals. In these forms the musculature is not 

 adapted to the quick and varied movement that we asso- 

 ciated with it in the higher animals, but it exhibits a con- 

 dition of prolonged contraction, a state of extended tonus, 

 such as is quite inconceivable in the skeletal muscles of a 



