GENERAL ZOOLOGY 



of public health are discussed frequently in the public press and are excellent 

 illustrations of the way in which basic scientific investigation is being applied 

 in the attempt to make our health more secure. 



Many other examples of applied science will occur to you. What, exactly, 

 is science? If you consult a dictionary, you will find that the word science 

 is derived from the Latin saentia, meaning knowledge. In modern usage, 

 science is knowledge gained by observation and reasoning; it is factual informa- 

 tion, correlated and systematized. One of the most important things that any 

 student of elementary science can learn is what is meant by the method of 

 science. This method is not the private property of scientists but has wide 

 application for anyone who will understand and use it. 



The knowledge we call science is based upon facts. A fact is the real state 

 of things, as distinguished from a belief. How do we determine what is a fact? 

 By observation, by the use of our sense organs. Science begins with sense per- 

 ceptions. We see that water changes to vapor as it boils; we feel the increasing 

 temperature of a wire held in a flame; we hear the call of a bird. Man has 

 made instruments of measurement in order to record his observations quanti- 

 tatively and to be able to compare them with those of other observers. It is 

 not profitable to argue about where the corn grows tallest or the buildings are 

 highest because both corn and buildings can be measured, and argument fails 

 to alter facts. The point to understand is that, whatever the branch of 

 natural science, observations on things are its raw materials. Wherever pos- 

 sible these observations are recorded quantitatively — things are counted or 

 measured. 



The scientist is not satisfied with the things nature shows him in her own 

 way. His curiosity is aroused by what she reveals, and he wants to know 

 more. Therefore he tries to think of a way to learn her secrets — he plans an 

 experiment. Naturalists before the time of Gregor Mendel had observed that, 

 when plants which differed in certain characteristics were cross-pollinated, 

 both types of plant reappeared in subsequent generations. Mendel planned 

 experiments in which he used plants that he had raised for several generations 

 and knew to be true breeding (p. 175). He made crosses between plants that 

 differed in only one respect, such as color of flower, length of stem, or color 

 of seed. When the offspring of these crosses appeared, he classified them and 

 recorded the number of each kind. After several years Mendel had a consider- 

 able number of recorded facts about the occurrence of these different plant 

 characters in the offspring of successive generations. He had the first accurate 

 data about the course of inheritance. 



The painstaking accumulation of data, the recording of facts, is only the 

 beginning of .science. What do the facts mean; do they have any relation to 

 other recorded facts? Mendel studied his data in order to find the meaning 

 of what he had observed during his experiments He found that he could 

 explain these facts of heredity by assuming the existence of units of inheritance 

 which behaved in definite ways. In other words, he formulated in his thinking 

 a hypothesis which correlated the facts he had observed. A hypothesis is not 



