INSTINCTS AND HABITS 247 



trates a very general fact about all protoplasm, or about living 

 things. Living things can get used to new conditions of temper- 

 ature, or of light, or of chemicals, or of food. This does not 

 mean that every living thing can come to live in any kind of 

 surroundings whatever. We know that is not true : birds can- 

 not get used to living in the water, fish cannot get used to living 

 in the air, plants and animals cannot get used to living without 

 proteins or without salts ; but the conditions of living can be 

 changed to a certain degree or in certain directions and the or- 

 ganism may still remain alive. Many substances modify the 

 activity of protoplasm in such a way that the protoplasm be- 

 comes dependent upon them. These so-called habit-forming 

 drugs are dangerous not only because of the immediate injury 

 they bring about but also because they make the victim require 

 increasing quantities and at last make him a slave in complete 

 dependence upon them. 



204. Importance of habit. The amount of work or play that 

 you can accomplish depends very largely upon the habits you 

 have acquired. In dressing yourself, how many movements are 

 necessary, and how much thought they take at first ! But now 

 you can dress yourself without thinking about the buttons and 

 sleeves at all. We ought to be able to do all of our toilet, and a 

 hundred other things that have to be done daily, or at least very 

 often, without giving the actions the slightest attention. This 

 means not only a great saving of time in doing necessary work ; 

 it means also a saving of thought for matters that are much 

 more interesting. 



The fact that animals form habits is made use of in many 

 ways in training animals to perform tricks for our entertain- 

 ment and in the everyday work of the farm or stable. By 

 regular programs of feeding and milking cows, for example, 

 we give them the habit of coming in from pasture when they are 

 wanted, either at sunset or when we call them, and this saves 

 the work of going after them; horses learn to follow fixed 

 routes, and they learn to come hom.e after they have strayed 

 away ; chickens come in response to a familiar call. 



