32 INDIVIDUALITY IN ORGANISMS 



highly specialized form, the nerve impulse, it probably 

 differs more or less widely from the initial change. 



The second point of importance in connection with 

 such transmission is the existence oi a decrement in 

 intensity or energy of the change in the course of its 

 transmission. Apparently a part of its energy is used 

 in overcoming a resistance or inertia or in producing 

 other changes which play no part in further transmission. 

 The existence of this decrement, which may be called 

 the transmission-decrement, determines that at a greater 

 or less distance from its point of origin the transmitted 

 change becomes inappreciable or ineffective, and trans- 

 mission does not proceed farther. In Fig. i the intensity 

 of excitation or the amount of increase in metabolic 

 activity is indicated diagrammatically for different 

 distances from the point of origin in a by the bands of 

 different width concentric at a. The limit of effective- 

 ness of transmission depends on the intensity or energy 

 of the original change produced at a and, secondly, upon 

 the character of the protoplasm. The higher the con- 

 ductivity of the surrounding protoplasm — in other words, 

 the less its resistance or the greater its sensitiveness to 

 the transmitted change — the greater the distance to 

 which the change will be transmitted before becoming 

 ineffective, and vice versa. In the existence of this 

 transmission-decrement the resemblance to the trans- 

 mission of waves in water and to various other forms of 

 physical transmission, such as electrical transmission, is 

 also apparent. A decrement in velocity of transmission 

 accompanies decrement in intensity, at least in certain 

 forms of transmission, but is not of primary importance 

 in the present consideration. 



