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INTRODUCTION 

 THE DOMAINS OF MORPHOLOGY 



Dass ich erkeniie, was die Welt 

 I»! Imiersten :^usammenhdlt. 



Goethe's Faust 



Morphological biology comprises the study of organs^ (anatomy 

 in medicine, organography according to Goebel), of tissues (histology) 

 and of cells (cytology). Together these domains form a hierarchic 

 system, since they describe units of diminishing size in the above 

 order. The diiferent domains defined by the concepts organ, tissue, 

 and cell can also be characterized by the expedients which are used 

 to make the units under investigation visible, since each of the three 

 sciences makes use of different instruments of observation. The 

 organographer observes with the naked eye or with the magnifying 

 glass, the histologist with the ordinary microscope and the cytologist 

 with the more refined immersion, phasecontrast (Zernike, 1946) or 

 even ultraviolet microscopes. Accordingly, the range of research of 

 organography is in general limited by the resolving power of the eye, 

 the domain of cytology by the resolving power of the microscope 

 (Fig. i). In biology, all that can be described with the aid of these 

 means of observation is referred to as morpholo^. 



The hierarchy of morphology, however, goes beyond the resolving 

 power of the microscope. The persistent, I might almost say the 

 heroic, struggle with which the resolving power of the microscope 

 has been increased (Abbe, 1879; Kohler, 1904) is the best evidence 

 of this. Fig. I shows how the microscopic domain was widened step 

 by step by advances in the theory and technique of optics until at about 



^ In this connection, "organ" is to be understood in the morphological sense as part 

 of an organism, and not in the physiological sense "organ = instrument", which is based 

 on specific functions; according to that definition, single tissues, special cells or even 

 parts of cells can also act as "organs". 



