INTRODUCTION 



A TEXT- BOOK of histology must have some very definite reason for 

 appearing at the present time when so many good books bearing that 

 title have appeared in the last few years and promise to continue to 

 appear. These books, however, with practically no exceptions, have 

 been intended for the medical school, and with this in view have been 

 restricted to the histology of man, as a main theme, with more or less 

 reference to other animals, principally the mammals. 



Such works have not filled the need of a text-book of general histology 

 for the college course, a book that treats of the principles of the subject. 

 They do not show what the animal cell is capable of as a builder of tissues 

 'which enable the organism to make use, more or less completely, of nearly 

 all the known forces of physics and many of those of chemistry. This 

 can be realized when we consider that they do not even mention such 

 tissues as produce electricity, light, gases, and many other things. And 

 again much is lost in the college course in histology by the fact that, of 

 those tissues which are treated of in the medical histology, the complete 

 significance is lost by not seeing their earlier representation and variation 

 in the lower forms. 



This volume has been written to secure a work that covers the general 

 field of histology and is not restricted in the main to human and mamma- 

 lian forms. It is intended to be a work that teaches general principles 

 and teaches histology as a pure science and for its own sake. It is 

 believed that it will serve as a broad foundation for future studies of 

 morphology and embryology as well as for the medical studies. 



As to method of treatment, it has seemed convenient to treat each 

 part, with some exceptions, by writing a general discussion of the subject, 

 and following this discussion with detailed laboratory descriptions of 

 types of the tissue, abundantly illustrated with good pen and ink drawings. 

 Such concrete examples have been selected from readily accessible 

 materials in most cases, and the proper procedure for securing and pre- 

 paring the materials has been indicated in small type at the end of each 

 chapter in many cases. In the last part of the book a chapter on technique 

 will be found, giving a short statement of principles and a guide for some 

 concrete practice. In some chapters the seminar work is not separated 

 from the statements of principles. Many instructors will see the ad- 



