234 THE TISSUES. 



10. Sexual Organs. 



11. Respiratory Organs. 



' The Spleen. 



10 T^ A1 j The Thyroid Body. 



12. Ductless Glands ^ n m J 



The Thymus Body. 



The Supra-Renal Capsules. 



13. The Organs of the Senses. 



In order, however, to avoid repetitions as far as possible, and to 

 proceed at the same time in the most intelligible manner, the first 

 seven tissues will be described in the following order ; after which 

 muscular tissue and the rest will follow in the order already given. 



1. Epithelium and its modifications. 



2. Yellow fibrous tissue. 



3. White fibrous tissue. 



4. Areolar tissue. 



5. Adipose tissue. 



6. Cartilage and Fibro-Cartilage. 



7. Osseous tissue and the Bones ; 

 Dental tissues, and the Teeth. 



8. Contractile or Muscular tissue, &c. &c. 



CHAPTER I. 



EPITHELIUM NAILS AND HAIK. 



THE epidermis and the nails have been by some authors termed 

 the horny tissues ; since, like the claws, horns, and hoofs of the lower 

 animals, and whalebone, so called, and tortoise-shell they contain 

 the immediate principle called Keratine (p. 100). Both these, how- 

 ever, and the epithelia of mucous and serous membranes, are histo- 

 logically so similar, that they will be described under the head of 

 epithelium; and the hair, next in order, as being an epithelial 

 appendage. 



All epithelial developments are destined to fall off, and thus be 

 lost to the organism, after accomplishing their proper functions ; 

 and they all consist of cells of various forms which have, in a mea- 



