GENERAL BIOLOGY 



cells being called Mesenchyme; later closely packed layers of 

 mesoderm cells may be formed that are known as Mesothelium. 



The cells of the different layers of the gastrula differ from one 

 another, and in the course of further development differentiations 

 appear among the cells of the same layer. In this way Tissues, i. e., 

 differentiated groups of like cells and their products. From the 

 two primitive tissues, epithelium and mesenchyme present in the 

 blastula and gastrula, all other tissues are derived, as shown here- 

 with. 



i. EPITHELIUM gives rise to 



a. Epithelial tissue 



b. Muscular tissue 



c. Nervous tissue 



d. Germinal tissue 



2. MESENCHYME gives rise to : 



a. Connective tissue 



b. Skeletal tissue 



c. Vascular tissue 



d. Storage (reserve) tissue 



These different tissues will be studied in the laboratory in con- 

 nection with each animal considered. 



The various functions of animal life, which in the Protozoa are 

 all performed by a single cell, are performed in the Metazoa not 

 only by many cells and tissues but also by groups of different 

 tissues united to form Organs, each with a specific function, and 

 by groups of organs united to form Systems, each having some one 

 general function, as shown in the following table : 



FUNCTIONS 



I. METABOLISM 



II. REPRODUCTION 



III. IRRITABILITY 



Ingestion 

 Digestion 

 Egestion 



Respiration 

 { Excretion 

 Circulation 



Assimilation 



Growth 



Dissimilation 



f Asexual 

 ( Sexual 



f Reception of 

 Stimuli 



| Transmission 

 of Stimuli 

 Coordination 



Movement 





ORGANS 



Mouth, Teeth 

 Stomach, Intestine 

 Anus 



Trachea, Lungs, etc. 

 Kidneys, Bladder, etc. 

 Heart, Arteries, Veins, etc. 



Have no special organs or sys- 

 tems 



No special organs or systems 

 Ovaries, Testes, Uterus 



Sense Organs 

 Nerves 



Ganglia, Brain 

 Muscles 



SYSTEMS 



Alimentary 



Respiratory 



Excretory 



Circulatory 



Genital 



Nervous 



Muscular 



[43] 



