536 



PHYSIOLOGY OF THE INVERTEBRATA. 



investigations it is evident, that the rate of transmission of 

 the motor nei'vous influx in its passage from nerve to muscle 

 fiads in the last nervous ramifications considerable delay. 



The following conclusions have been arrived at by Fredericq 

 and Vandevelde : — 



(1) There appears to be a complete identity in the pro- 

 perties of the muscles of Homarus and those of Rana. 



(2) The motor nerves of Homarus present, from o, physio- 

 logical jyoint of view, great points of resemblance to those of 

 Bana. The most characteristic difference consists in the 

 slowness with which the motor excitation travels the length 

 of the motor nerves. In Homarus it is 6 metres, and in 

 Bana 27 metres per second. The slow rate of transmission 

 of the motor excitation proves in Homarus a considerable 

 slackening in the muscular terminations of the motor nerves. 



The difference in the rate of transmission may be due to 

 the difference in the composition of the nervous matter of the 

 two animals. The following table represents the chemical com- 

 position* of the nerves of Homarus and Bana respectively : — 



Dr. A. B. Griffiths' analyses. 



