176 GENERAL BIOLOGY 



Again the student must be cautioned not to let. one side of a prob- 

 lem cause him to discard much that is of value in opposing schools of 

 thought. 



Just as those who are primarily interested in nothing but anatomy 

 are likely to leave out important functional causes in a disease, so those 

 primarily interested in physiology are likely to forget the structural ele- 

 ments which may contribute points of tremendous importance. 



All schools of science have been drilling into the student the sup- 

 posed "fact" that "Structure determines Function," but since the very 

 recent work of Carey, who converted unstriated bladder-muscle of a liv- 

 ing dog into living heart-muscle by simulating heart conditions in the 

 bladder, we must insist that function has just as important a part in 

 changing and determining structure as structure has in determining 

 function. 



However, we must not forget that even in the case just mentioned,, 

 the substance to be changed was already present and must have pos- 

 sessed the potentiality of change before it could be worked upon. 



With this introduction we can the better understand the two ways 

 in which the study of comparative psychology is approached by the 

 modern laboratory worker. First, we may take a highly developed indi- 

 vidual, such as man, and after analyzing his mental-world, apply the 

 knowledge thus gained to the lower forms, or 



Second, we may follow up, step by step, the increasing learning- 

 ability on the part of all phyla of animals, beginning with the unicellular 

 and passing upward through an ever-increasing scale of ability. 



It is this second method which seems to have found most favor with 

 animal psychologists. 



But, in reading works on animal psychology, one is always con- 

 fronted with a great confusion of terms. In fact, one finds here the 

 same difficulties that confront the student in any of the biological sci- 

 ences. The first workers in all these fields were philosophers, and were 

 interested primarily, and sometimes only, in the human family. The 

 terms, therefore, which these men used, although worked out with great 

 precision, applied only to man. 



The newer writers took many of the older labels and placed them 

 on new bottles, so to speak. This has caused a world of confusion, not 

 only to new students, but to many well versed in language and litera- 

 ture. 



Such words as Mind, Intelligence, Reason, Memory, Consciousness,, 

 Sensory or Associative Memory, Instincts, and Reflex Actions, are some 

 of the terms which the student must use, and which have many con- 

 flicting meanings in modern literature. It is imperative that the student 

 obtain a clear and concise definition of these terms and use them only 

 in this restricted sense. Then only can he understand the meaning 

 which different writers assign these words, and then only can he know 



