FIBKOUS TISSUE. 227 



When examined under the microscope, the areolar tissue is 

 seen to be principally made up of exceedingly fine transparent 

 and apparently homogeneous filaments, from about 1-1 5,000th 

 to l-25,000th part of an inch in thickness. These are for the 

 most part united by means of a small quantity of clear homo- 

 geneous connecting substance into bundles and filamentous 

 laminae of various sizes, which, to the naked eye, appear as 

 simple threads and films. The bundles intersect in every direc- 

 tion, yet the filaments of the same bundle run nearly parallel 

 to each other, and no filament is seen to divide into branches, 

 or to become continuous with another. The united filaments 

 take an alternate or waving course without losing their paral- 

 lelism. Such filaments not only belong to the areolar tissue 

 strictly so called, but form the chief part of the tendons, 

 ligaments, and other white fibrous tissues. 



Intermixed with these filaments of the areolar tissue are 

 yellow elastic fibres which seem to be identical with the fibres 

 of the proper yellow elastic tissue. 



The areolar tissue contains a large proportion of fluid, so as 

 to lose much weight by drying. By boiling it is resolved almost 

 entirely into gelatine. 



Fibrous Tissue. The fibrous tissue forms the ligaments of 

 the joints, the tendons of the muscles, and, assuming the mem- 

 branous character, it constitutes the fibrous membranes. Of 

 these the chief are the periosteum, the perichondrium, which 

 cover the bones and cartilages, the layer of the dura mater 

 next the skull, and the fibrous layer which strengthens the peri- 

 cardium. To these may be added the albugineous coat of the 

 testicle and that of the ovary, and the sclerotic coat of the eye. 

 Fibrous expansions under the name of aponeuroses or fasciae bind 

 down the muscles for example, the great fascia enclosing the 

 muscles of the thigh and leg. The tendons of muscles, as those 

 of the broad muscles of the abdomen, may present the expanded 



