PART I. 

 VEGETABLE PHYSIOLOGY. 



LESSON I. 



INTRODUCTION. 



1. Physiology, or the science which teaches the functions of all 

 the different parts or organs of animals and plants ; or the offices 

 which they perform in the economy of the individual ; or, in other 

 words, the science of life, is daily esteemed of greater importance. 



2. Physiology, as now understood, has become quite a modern 

 science, and one that owes its great advancement and chief excel- 

 lence to the Microscope alone. 



3. Without its invaluable aid, our notions and opinions would be 

 as crude, unsatisfactory, and erroneous, as were those of our fore- 

 fathers. Before its mighty presence every fragment of a tissue is 

 bound to succumb ; it has no preconceived theory to support ; it is 

 called upon to do but one thing to assist us in our researches, and 

 nobly it does it ! it tells the truth, whereby the laws of physiologi- 

 cal science are rendered as certain as a problem in Mathematics. 



4. The Microscope has originated a new science Histology 

 from two Greek words, which signify a " discourse on tissues ; " now 

 what is a tissue ? Webster's definition is as follows : " in anato- 

 my, texture or organization of parts. The peculiar, intimate struc- 

 ture of a part is called its tissue. A part of a fibrous structure is 

 called a fibrous tissue. The organs of the body are made up of 

 simpler elements, some generally diffused through the body, and 

 others peculiar to particular organs. These simpler structures are 

 called the tissues of the body ; as, the cellular tissue, the mucous 

 tissue, &c." 



1 



