476 



appear at first glance to be widely different. These are: (a) amor- 

 phous substances; (b) fibers; (c) cells. 



(a) Amorphous substances may be in liquid form, as in the fluid of 

 the blood, which holds a vast amount of salts and nutritive matter in 

 solution, or they may be in a semi-liquid condition, as the plasma 

 which infiltrates the loose meshes of connective tissue and lubricates 

 the surface of some membranes, or they may be in the form of a glue 

 or cement, fastening one structure to another, as a tendon or muscle 

 end to a bone, or again they hold similar elements firmly together as 

 in bone, where they form a stiff matrix which becomes impregnated 

 with lime salts. Amorphous substances again form the protoplasm 

 or nutritive element of cells or the elements of life. 



(&) Fibers are formed of elements of organic matter which have 

 only a passive function. They can be assiuiilated to little strings or 

 cords tangled one with another like a mass of waste yarn, woven regu- 

 larly like a cloth or bound together like a rope. They are of two 

 kinds, white connective tissue fibers, only slightly extensible, pliable, 

 and very strong, and yellow elastic fibers, elastic, curly, ramified, and 

 very dense. These fibers once created require the constant presence 

 of fluids around them in order to retain their functional condition, as 

 a piece of harness leather demands continual oiling to keep its 

 strength, but they undergo no change or alteration in their form until 

 destroyed by death. 



(c) Cells, which may even be regarded as low forms of life, are 

 masses of protoplasm or amorphous living matter with a nucleus and 

 frequently a nucleolus or living germs, which are capable of assimi- 

 lating nutriment or food, propagating themselves either into others of 

 the same form or into fixed cells of another outward appearance and 

 different function, but of the same constitution. It is simply in the 

 mode of grouping of these elements that we have the variation in tis- 

 sues, as: (1) loose connective tissue ; (2) aponeurosis and tendons; (3) 

 muscles; (4) cartilage; (5) bones; (6) epithelia and endothelia; (7) 



nerves. «. i v 



(1) Loose connective tissue forms the great framework or scaffolding 

 of the body, and is found under the skin, between the muscles sur- 

 rounding the bones and blood vessels, and entering into the structures 

 of almost all of the organs. In this the fibers are loosely meshed 

 together like a sponge, leaving spaces in which the nutrient fiuid and 

 cells are irregularly distributed. This tissue we find in the skm, m 

 the spaces between the organs of the body where fat accumulates, 

 and as the framework of all glands. 



(2) AiJoneuTOsis and tendons are structures which serve for the ter- 

 mination of muscles and for their contention and for the attachment 

 of bones together. In these the fibers are more frequent and dense 

 and are arranged with regularity, either crossing each other or lying 

 parallel, and here the cells are found in minimum quantity. 



