VEGETAL AND ANLVAL PROTOPLASM. 41 



nature of its connection with the other elements or compounds 

 present. 



Electricity. It has been shown that many forms of vital 

 action are accompanied by electrical disturbances in the proto- 

 plasm. It is therefore not surprising that the application of 

 electricity to living protoplasm should have a marked effect on 

 its actions. If the stimulus be very slight, protoplasmic move- 

 ments are favored. Colorless blood-corpuscles creep more actively, 

 and ciliary action increases in vigor. Stronger shocks cause a 

 spasmodic contraction of the protoplasm (tetanus), from which it 

 may or may not be able to recover, according to the strength of 

 the shock. 



Poisons. Towards certain agents protoplasm is indifferent 

 or seemingly so, but towards others it behaves in a very remark- 

 able manner. The matters known as poisons modify or destroy 

 its activitv, as is well known from the familiar effects of arsenic, 



/ ' 



opium, etc. Disease may also interfere with its normal activity ; 

 but the consideration of these phases of the subject belongs to 

 the more exclusively medical sciences, such as toxicology aud 

 pathology. 



Other physical agents. The more highly specialized forms 

 of protoplasm are affected by a great variety of physical agents, 

 such as light, sound, pressure, ere., and upon this susceptibility 

 depend many of the higher manifestations of life. For instance, 

 waves of light or of sound, acting upon special protoplasmic 

 structures in the eye and ear, call forth actions which ultimately 

 result in the sensations of sight and hearing. Similar consider- 

 ations apply to the senses of smell, taste, and touch ; but the dis- 

 cussion of all these special modes of protoplasmic action must be 

 deferred. Enough has been said to show that living organisms 

 (that is, the protoplasm which is their essential part) are able to 

 respond to many influences proceeding from the world in which 

 they live. Upon this property depend the intimate relations be- 

 tween the organism and its environment, and the power of adapt- 

 ability to the environment, which is one of the most marvellous 

 and characteristic properties of living things. 



Vegetal and Animal Protoplasm. The protoplasm of plants is 

 essentially identical with that of animals in chemical and physical 

 relations, and manifests the same fundamental vital properties. 



