DIONiEA MUSCIPULA. 381 



shows symptoms of decay. The phenomena seem to resemble very 

 much those which take place in animals in whom food is subjected to 

 the action of ptyaline in the mouth and of pepsine in the stomach, 

 along with the formation of hydrochloric acid. Both in the leaf and 

 in the animal stomach an acid is formed with the view of promoting 

 digestion. The plant has therefore been called insectivorous and 

 carnivorous, as requiring the presence of albuminous animal food for 

 its growth and nutrition. There is marked irrito-contractility ; first 

 irritation and then contraction. Every living substance is capable of 

 being excited into action — that is, of having its stored-up force dis- 

 charged. There is a change of form, seen usually in some mechanical 

 work. There seems, as Dr. Burdon Sanderson remarks, to be a 

 resemblance between the contraction of muscle and the contraction of 

 a leaf. The muscle exhibits chemical changes, consisting in disinte- 

 gration of chemical compounds and dissipation of force stored up in 

 these compounds. These phenomena are more especially seen when 

 muscle contracts and when heat is developed. 



The muscle in its living state is electro-motive, and the force 

 depends on the vigour of the muscle. When the muscle and the leaf 

 contract, electro-motive force disappears and work is done. There is, 

 however, no conversion of the one into the other, and there is no 

 evidence that the force is electrical. 



Dr. Burdon Sanderson gives the following account of the elec- 

 trical phenomena which accompany irritation of the leaf of Dionsea : — 



" 1. When the opposite ends of a living leaf of Dionsea are placed on 

 non-polarisable electrodes in metallic connection with each other, and 

 a Thomson's reflecting galvanometer of high resistance is introduced 

 into the circuit thus formed, a deflection is observed, which indicates 

 the existence of a current from the proximal to the distal end of the 

 leaf. This current I call the normal leaf-current. If, instead of the 

 leaf, the leaf-stalk is placed on the electrodes (the leaf remaining 

 united to it) in such a way that the extreme end of the stalk rests on 

 one electrode; and a part of the stalk at a certain distance from the 

 leaf on the other, a current is indicated, which is opposed to that 

 in the leaf. This I call the stalk-current. To demonstrate these two 

 currents, it is not necessary to expose any cut surface to the electrodes. 



"2. In a leaf with the petiole attached, the strength of the cur- 

 rent is determined by the length of the petiole cut off with the leaf, 

 in such a way that the shorter the petiole the greater is the deflec- 

 tion. Thus, in a leaf with a petiole an inch long, I observed a deflec- 

 tion of 40. I then cut off half, then half the remainder, and so On. 

 After these successive amputations, the deflections were respectively 

 50, 65, 90, 120. If in this experiment, instead of completely sever- 

 ing the leaf ait each time, it is merely all but divided with a sharp 

 knife, the cut surfaces remaining in accurate apposition, the result is 



