ANIMAL CELLS. 



5 



Ectoderm 



or 

 Epiblast. 



Mesoderm 



or 

 Mesoblast. 



Entoderm 



or 

 Hypoblast. 



The epithelium of the skin or epid 

 sebaceous and sweat glands. 



cesses combined. The cells which are least altered from their embryonic condition 

 are the white corpuscles of the blood, and these may be regarded therefore as 

 typical cells. 



The histogenetical relation between the three layers of the blastoderm and the 

 several tissues and organs of the body is exhibited in the following table : 



ermis, and its appendages, viz., the hairs, nails, 



The epithelium of the mouth, and of the salivary and other glands which open 

 into the mouth. The enamel of the teeth. The gustatory organs. 



The epithelium of the nasal passages, and the cavities and glands which open 

 into them. 



The epithelium covering the front of the eye. The cystalline lens. The retina. 



The epithelium lining the membranous labyrinth of the ear. 



The epithelium lining the central canal of the spinal cord, the aqueduct of Syl- 

 vius, and the fourth, third, and lateral ventricles of the brain. 



The tissues of the nervous system. 

 i^The pituitary body. The pineal gland. 



The connective tissues. 

 The blood- and lymph-corpuscles. 



The epithelial lining of the heart, blood-vessels, lymphatics, and serous mem- 

 branes (endothelium). 



The epithelium of the uriniferous tubules. 



The epithelium of the generative organs, and the generative products in both sexes. 

 The muscular tissues, voluntary, involuntary, and cardiac. 

 The spleen and other lymphatic and vascular glands. 



/The epithelium of the alimentary canal (from the pharynx to the lower end of the 

 rectum) and all the glands which open into it (including the liver and 

 pancreas). 

 J The epithelium of the Eustachian tube and cavity of the tympanum. 



I The epithelium of the larynx, trachea, and bronchi, and of all their ramifications. 

 The epithelium of the pulmonary alveoli. 



I The epithelium of the thyroid body. The concentric corpuscles of the thymus gland. 



* The epithelium of the urinary bladder. 



