PREFACE 



In the preparation of this text-book of Histology we have kept fore- 

 most in mind the needs of medical students as we have come to under- 

 stand them in our experience as teachers of the subject. These needs 

 have been suggested by the common difficulties we have discovered on 

 the part of the average student. It has been our effort to lessen these 

 difficulties in the most practical way. Our experience has demonstrated 

 to us the efficacy of the methods here pursued. 



The bulk of the subject matter of Histology is now relatively stable. 

 With respect to this nucleus our problem has largely been one of the best 

 means of presentation. The secret of success in the acquisition of his- 

 tologic data is of course fundamentally an interest in the subject. In- 

 terest can best be stimulated by a revelation of relationships to future 

 more clearly conceived practical ends; and it can best be sustained by 

 the possession of principles and generalizations that serve at least pro- 

 visionally to coordinate the mass of seemingly unrelated facts. These 

 considerations force an approach to the subject of Histology largely from 

 the viewpoint of function. The known or believed function dependent 

 upon the structure described is therefore briefly indicated whenever this 

 seems desirable. With the same e^d in view comparative anatomic and 

 embryologic facts are frequently presented. 



Since Embryology usually constitutes a separate course of the med- 

 ical curriculum, the development of tissues and organs is discussed only 

 to the extent deemed absolutely essential for a proper appreciation of 

 structure. Since the anatomy of the Nervous System likewise properly 

 constitutes a separate course, only the nervous tissues are here described, 

 including the microscopic structure of the spinal cord, the cerebral cor- 

 tex and the cerebellar cortex. A description of the structure of the 

 brain stem is not included. An effort has been made to include the 

 results of the latest investigations especially as regards cytologic data, 

 particularly in relation to the genital glands. The organs of internal 

 secretion are treated under a single head, and rather more fully, in view 

 of their now evident importance, than has hitherto been the case. 



The illustrations have been taken from various sources, duly cred- 



