A TEXT-BOOK OF HISTOLOGY 



CHAPTER I 



INTRODUCTION PROTOPLASM CELL 



INTRODUCTION 



Definition of Histology. Histology is the science of tissue struc- 

 ture, plant or animal. It concerns itself, therefore, chiefly with the 

 structural characteristics and interrelationships of the component ele- 

 ments of tissues. These elements are the cells, and the material con- 

 necting or separating the cells, the intercellular substances. A tissue 

 consists of cells associated in the performance of 

 a specific function. A cell may be defined in a 

 preliminary way as the unit of organic structure 

 and function. The minuter details of histology 

 involve also cell anatomy or cytology. Here we 

 meet witli the essential substance of the cells, the 

 protoplasm, or bioplasm, the 'material basis of life/ 

 We also meet with the chief 'organ' of cells, the 

 nucleus. A completer definition of a cell may 

 accordingly be given as a circumscribed mass of 

 protoplasm containing a nucleus (Fig. 1). A com- FIG. 1. VARIOUS 

 plete histologic description embraces, therefore, SPHEROIDAL CELLS 



details of the" relationships of the component cells f *> fr m ovai T 



of a child; 2, sperm- 



ot a tissue and of the protoplasmic structure, and atocyto; and 3, sperm- 

 nuclear characteristics of the types of cells in- atid, from the testicle 



Yoked. Histology includes further a knowledge of f . a rab . bit - . Hema ' 



. c tern and cosm. X 



tissue origin and development, or lustogenesis, and 759. 



of cell origin and development, or cytogenesis. 

 Cells are the 'building stones' of tissues ; tissues combine to form organs ; 

 organs are associated into systems. Histology is accordingly a part of 

 general anatomy; it is tissue anatomy ; that part of histology \vhich con- 

 siders the relationships between tissues in organs is sometimes spoken of 

 as microscopic anatomy. 



2 1 



