1898] RUDIMENTARY NERVOUS SYSTEM 339 



extremities and tie it by the other to a weight that can easily slide 

 on a polished surface. At the vibration of the tube, that must be 

 stretched beforehand, the weight is drawn by a quantity equiva- 

 lent to the extent of the vibration. (Figs. 13 and 14.) 



2. By previously stretching a tube it may be induced to 

 vibrate if connected in a point on its middle with a large 

 globule of mercury (nervous termination), the vibrations of which 

 start those of the tube ; the locomotion of the weight along the 

 table is the issue of all this. (Figs. 13 and 14.) 



This experiment may be considered as a difficult one on account 

 of the computations indispensable to determine the degree of length 

 of the tube and that of the weight which it must attract. 



Perhaps the vibration of a muscle is due to the discharges of 

 carbonic oxide. 



(c) Acceleration of the pulsatile wave as observed by Landois 

 in elastic tubes previously filled with water. — This too is easily 

 observed in threads of mercury and serves to elucidate the question 

 concerning certain reflexes that are simply the result of several suc- 

 cessive excitations (ejaculation). A. L. Herrera. 

 Mexico, May 1st, 1898. 



(To be continued) 



