18 HAND-BOOK OF PHYSIOLOGY. 



them; while these again are variously mixed and interwoven to form 

 more intricate combinations. 



Thus are constructed epithelium and its modifications, connective 

 tissue, fat, cartilage, bone, the fibres of muscle and nerve, etc. ; and these, 

 again, with the more simple structures before mentioned, are used as 

 materials wherewith to form arteries, veins, and lymphatics, secreting 

 and vascular glands, lungs, heart, liver, and other parts of the body. 



