22 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



Histology is the science that treats oi cells and 

 their products, therefore it is largely a study of 

 protoplasm. The fundamental principles of thera- 

 peutics are based upon the action of drugs on proto- 

 plasm, Pathology involves a recognition of micro- 

 scopic changes, other than normal, in living matter. 

 Physiology has much to say about the actions and 

 products of this same substance. Embryology 

 traces the developmental history of protoplasm to 

 form tissues, organs, and a new living being. It is 

 this great importance of protoplasm, and partic- 

 ularly its relation to histology, that has prompted 

 these introductory remarks. 



