THE VITAL PROPERTIES OF THE CELL 113 



are employed medicinally, the attempt is made to act upon the 

 nervous system alone, for if all the elementary cells were affected, 

 a cessation of the vital processes would result, and death might 

 ensue. However, the following examples will prove clearly that 

 the irritability of animal and vegetable protoplasm may be 

 temporarily destroyed without permanent harm. 



The sensitive plant, or Mimosa pudica, is very easily affected by 

 mechanical stimulation. When a leaflet is shaken a little, it 

 immediately closes itself up, and forsaking its upright position, 

 droops downwards. In addition, it forms an example of the rapid 

 manner in which a stimulus is conducted in plants, in which, since 

 no nerves are present, it must be simply transmitted by each pro- 

 toplasmic cell quickly conveying the impulse to its neighbour. 

 In consequence of this, if the stimulus is sufficiently strong, not 

 only do the leaves which were directly touched close up, but also 

 those on the same branch, and eventually even the whole plant, 

 are affected. In consequence of the stimulation, certain mechanical 

 arrangements, not suitable for present discussion, come into play. 



In order to study the effect of anaesthetics, a sensitive plant, in 

 a condition of normal irritability, should be placed under a bell- 

 jar, and when the leaves are fully extended, a sponge soaked with 

 _ chloroform or ether should be inserted (Claude Bernard IV. 1). 

 After about half an hour it is seen that the chloroform or ether 

 vapour has caused the protoplasm to lose all its irritability. 

 When the bell-jar is removed, the leaves, which are spread out 

 as usual, may be touched, or even severely crushed or cut, without 

 any reaction being produced ; the result is the same as that pro- 

 duced on one of the higher animals provided with nerves. And 

 yet, if proper precautions have been taken, it is found that the 

 protoplasm has not been killed, for after the sensitive plant has 

 been for a short time in the fresh air, the narcosis gradually 

 disappears; at first, individual leaves gradually close up when 

 they are roughly handled, until finally complete irritability is 

 restored. 



Ova and spermatozoa may be subjected to the action of narcotics 

 in a similar manner. When Richard Hertwig and myself (IV. 12a) 

 placed the actively motile spermatozoa of a sea-urchin in a '5 per 

 cent, solution of chloral-hydrate in sea water, we found that after 

 five minutes, their motions were completely arrested; however, 

 these soon recommenced, after the chloral solution had been diluted 

 with pure sea water. Further, those spermatozoa which had been 



i 



