TECHNIQUES OF ANATOMY — ROOFE AND LESHER 329 



EMBRYOLOGY 



A knowledge of embryology is fundamental to the understanding 

 of the adult organism. The foundation for the science of embryology 

 was laid by Aristotle through his original observations and theoretical 

 acumen. It was he who said that if one wishes to understand the 

 present structure, one must study its past evolutionary history. Karl 

 Ernst von Baer (1792-1876) is, in the modern sense, considered the 

 father of descriptive embryology. This early phase of embryology 

 was predominantly descriptive of the changes in form and structure 

 during development. However, since embryology is not a static 

 science but one that is alive and dynamic, it is not looked upon as a 

 science dealing with structure alone, but with form and function. 

 Embryology then, has paved the way to an understanding of how the 

 adult organism reached maturity. 



In addition to morphology, embryology has made valuable contribu- 

 tions to our understanding of developmental behavior. In this realm 

 George E. Coghill (former head of the University of Kansas Depart- 

 ment of Anatomy) laid the basic groundwork. His study of the de- 

 velopment of the nervous system in the larval form of Ambystoma 

 tigrinwm, a primitive land vertebrate belonging to the salamander 

 group, showed that behavior was not the welding together of individ- 

 ual reflex arcs as they appeared in the embryo, but that the organism 

 behaved as a whole and that discrete individual reflexes emerged out 

 of this total behavior pattern. This work began in 1913 and con- 

 tinued until Coghill's death in 1941. His contributions were signifi- 

 cant in other fields than the straight morphological study of the de- 

 veloping embryo. 



Psychologists and philosophers were eager and keen to grasp the 

 meaning of Coghill's contribution to the study of behavior. He 

 showed that in the development of any organism the anatomical and 

 neurological structures came into being far in advance of their func- 

 tional capacity. Since Coghill's study of the development of Ambys- 

 toma, similar research has been undertaken in higher organisms in- 

 cluding man. It is generally held by those working in the field that 

 Coghill's conception of behavior holds true in all forms. Davenport 

 Hooker, of the University of Pittsburgh, working for the past 20 years 

 on embryonic and fetal development in man, has shown that the Cog- 

 hillian principles of development hold here also. The over-all picture 

 of these findings indicate clearly that all organisms develop in an in- 

 tegrating field, and during the course of this orderly development dis- 

 crete movements emerge which are always under the dominance of the 

 total organism. 



The picture of man's development from the single fertilized ovum 

 to the fully formed adult is gradually coming into focus. Important 



