24 THE FUNCTIONS OF ANIMALS. 



by stimulus, the one tending to storage, construction, assimilation of 

 material, the other tending to explosion, disruption, disassimilation. 

 Both processes are, according to Hering, activities ; both are dependent 

 upon stimulus ; they differ, however, in direction and results. 



In your future jDhysiological studies, you will also learn of the paths 

 or channels by which the brain sends its mysterious commands to the 

 various parts of the body. You will learn that some of these bear 

 impulses to activity, while others convey commands which send the 

 affected part to rest. 



It was in studying and greatly elucidating these interesting facts, that 

 Professor Gaskell was led to a theory of vital action somewhat different 

 from that of Hering. 



Gaskell believes that life means an alternation of two processes, one of 

 them a running down or disruption (katabolism), the other a winding 

 up or construction (anabolism). The disruptive or katabolic process in 

 which energy is discharged, takes place occasionally and in obedience to 

 stimulus ; the constructive or anabolic process of restitution goes on con- 

 stantly and of itself, z.<f., without thenecessity of stimulus. Thus Gaskell's 

 theory suggests an alternation of activity and rest, of stimulated disruption 

 and self-regulative construction, while Hering's theory suggests an 

 alternation of two antagonistic kinds of activity, assimilation and dis- 

 assimilation, both requiring stimulus. The student will find the theories, 

 which I have briefly noticed, discussed in Professor M. Foster's article 

 Physiology, in the Encyclopadia Britannica, and in an address by 

 Professor Burdon Sanderson (British Association Reports, 1889, and 

 also published in Nature, September 1889). 



