CONSClorSXESS AND PAIN 75 



knocked over with a mortal blow. Every or- 

 ganism, except when in a special state of re- 

 pose — for instance, during the hibernation of 

 some animals and the period of a plant's ex- 

 istence when enclosed in a seed — every organ- 

 ism of whatever grade of development is 

 possessed of sensitiveness of essentially the 

 same character as that of the simplest bit of 

 protoplasm revealed b^^ the microscope. As 

 the organism rises in the scale of being, 

 irritability- takes on a correspondingly varied 

 development. And it may be asserted that 

 the recoil when I accidentally press my hand 

 against a thorn is of the same essential 

 nature as that of an amoeba or slime-mold 

 when pierced with a sharp point; or that the 

 so-called instinct of the dog which urges him 

 to follow up the scent of a rabbit when hun- 

 gry, has its basis in the same fundamental 

 property- of living matter as that which 

 causes the lively spores of the salmon-fungus 

 {Saprolegnia) to swim toward the spot from 

 which there is a slight emanation of decaying 

 fish, or the leaf-mildew to turn and grow 

 toward the breathing pore of a grape leaf, in- 

 to which it desires to enter and find a congen- 

 ial place of development, because it detects a 

 slight escape of vegetable acids from that di- 

 rection. 

 Irritability in its various forms must, there- 



