HISTOLOGY. 



37 



OF THE TI SSUES. 



The solids of an animal body have been divided into tissues, any one 

 of which presents the same characteristics, no matter in what portion of 

 the body it is found. The tissues may be further divided into simple and 

 compound tissues ; meaning by compound those which consist of two or 

 more simple or elementary tissues mixed together in a definite and regular 

 manner. As an instance of this we may mention fib ro- cartilage, which 

 consists of a net- work of white fibrous tissue, having its meshes or inter- 

 stices filled up by a cartilaginous deposit. 



The simplest form of animal organism is Fig. i.* 



the nucleated corpuscle or cell, which is a 

 little vesicle or bag, containing a fluid in its 

 early stage, and a granular body called a 

 nucleus, attached to some portion of the cell 

 wall. This nucleus occasionally presents 

 one or two distinct corpuscles in its sub- 

 stance, which when found are called nucle- 

 oli, and which possibly are the germs of new 

 cells. 



Every portion of the animal organism is 



formed by these cells, and as the body is undergoing constant repro- 

 duction and decay, they are found in various stages of development 

 at any time in the life of an animal. 



DIVISION OF THE TISSUES. 



The animal organism may be divided into simple, or non-metamor- 

 phosed forms, and compound, or metamorphosed forms of animal matter. 

 They are presented in the following tabular form : 



1. SIMPLE FORMS: 



1. Nucleated cells, 



2. Corpuscles, 



1. Formative, producing solids (durable}. 



2. Secreting, producing fluids (evanescent). 



1. Of the blood, 



2. Of the lymph, 



3. Of the chyle. 



2. COMPOUND FORMS: 



Tissues produced by the metamorphosis of cells. They ara divided 

 into simple and compound tissues. 



Simple Tissues: 



1. Epithelial tissue, 



presenting several < 



1. Simple membrane, 



2. Pigmentary membrane, 



3. Tesselated epithelium, 



varieties. f Cylmdroid epithelium, 



o. Ciliated epithelium, 

 t>. Aggregated epithelium, 



2. White fibrous tissue (inelastic). 



3 Yellow fibrous tissue (elastic). 



* A group of vegetable cells. ]. Nucleus. 2. Nucleoli in nucleus. 



