28 • PSYCHOBIOLOGY 



within the bone it manufactures, is called a bone cell [Fig- 17]. Car- 

 tilage is formed as the thick cell walls secreted by the cartilage cells 

 [Fig. 16]. 



4. Nerve tissue comprises the essential portions of the ' nerves ', spinal 

 cord, brain, and other ganglia, and is derived wholly from the ectoderm. 



5. Muscle. Smooth or non-voluntary muscle develops from the 

 mesenchymal cells of the mesoderm. Striped or voluntary muscle de- 

 velops from the non-mesenchymal cells of the mesoderm. 



6. Vascular tissue. This includes the blood and lymph, and the essen- 

 tial elements of the lymph glands and the red marrow of the bones, and' 

 develops from the mesoderm. 



7. Glands. The active tissues in these are composed of modified epi- 

 thelial cells. Glands are developed from all three blastodermic layers. 



Nervous, muscular, and glandular tissues will be treated more fully in 

 the following chapters. 



REFERENCES ON TISSUES GENERALLY. 



Schafer, Microscopic Anatomy, § Structure of the Tissues, Sub-§§ The Elementary- 

 Tissues, The Epithelial Tissues, Connective Tissue. 



Bailey, Histology, Part III, Chapters MIL 



Lewis and Stohr, Histology, Pt. I, § II, Sub-§§ Histogenesis, Epithelium, Meser*- 

 chymal Tissue. 



Hertwig, Manual of Zoology, § General Anatomy, II. 



