GENERA^ DEFINITIONS. 47 



day is that all physiological phenomena (excepting those of 

 consciousness, possibly) may be explained in terms of 

 chemistry and physics. Thus, what uses organs and tissues 

 have, becomes a physical and chemical question in essence 

 rather than a biological one. 



ANATOMY. 



Before, however, vital phenomena can be studied, it is 

 necessary that we should know the structure of the body 

 exhibiting these phenomena; and so physiology must 

 always be logically preceded by the study of anatomy. As 

 these phenomena usually exhibit themselves in the ultimate 

 biological structure of tissues and organs, anatomy must be 

 extended with the aid of a microscope to the minute struc- 

 ture of every part. The study of this minute structure is 

 designated as histology. 



COMPARATIVE ANATOMY. 



After the structure of the body in question is known, 

 and the function of the various parts established, and pos- 

 sibly even some notion gained as to the care that ought to 

 be exercised in properly preserving it, that is, its hygiene 

 understood, our knowledge is still very inadequate. We 

 must compare the form in question with other animal forms, 

 for the most helpful knowledge of anything is frequently 

 that which deals with the relations of that thing to others. 

 Thus, the study of comparative anatomy helps to materi- 

 ally clarify the individual anatomy in question. 



EMBRYOLOGY. 







But even this information is inadequate. Even when 

 we have made extended comparisons with the related forms 

 much is still left unsolved until we know how this individual 

 structure came to be. The science which seeks the 

 sequence of changes which finally leads to the adult form 

 from its primitive beginning in the egg, is the science of 

 embryology. 



