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of supporting and connecting the tissues of the frame. These tissues may differ 

 considerably from each other in external appearance, but they present neverthe- 

 less many points of relationship with each other, and are moreover developed 

 from the same embryonal elements. They are divided into three great groups: 

 (1) the fibrous connective tissues, (2) cartilage, and (3) bone. 



The Fibrous Connective Tissues. Three principal forms or varieties of fibrous 

 connective tissue are recognized : (1) White fibrous tissue ; (2) Yellow elastic 

 tissue: (3) Areolar tissue. They are all composed of a matrix in which cells are 

 imbedded, and between the cells are fibres of two kinds, the white and yellow or 

 elastic. The difference between the three forms of tissue depends on the relative 

 proportion of the two kinds of fibre, in the first variety enumerated the white fibre 

 preponderating ; in the second variety the yellow elastic fibres being greatly in 

 excess of the white ; and the third form, areolar tissue, the two being blended in 

 much more equal proportions. 



The white fibrous tissue (Fig. 13) is a true connecting structure, and serves 

 three purposes in the animal economy. It serves to bind bones together in the 

 form of ligaments, it serves to 

 connect muscles to bones or 

 other structures in the form of 

 tendons, and it forms an invest- 

 ing or protecting structure to 

 various organs in the form of 

 membranes. Examples of 

 where it serves this latter office 

 are to be found in the muscular 

 fasciae or sheaths, the perios- 

 teum, and perichondrium ; the 

 investments of the various 

 glands, (such as the tunica 

 albuginea testis. the capsule of 

 the kidney, etc.). the investing sheath of the nerves (epineurium). and of various 

 organs, as the penis and the eye (sheath of the corpora cavernosa and corpus 

 spongiosum, and of the sclerotic). But in all these parts the student must bear in 

 mind that the elastic tissue enters in greater or less proportion. It presents to 

 the naked eye the appearance of silvery-white glistening fibres, covered over with 

 a quantity of loose, flocculent tissue which binds the fibres together and carries 

 the blood-vessels. It is not possessed of any elasticity, and only the very 

 slightest extensibility ; it is exceedingly strong, so that upon the application of 

 any external violence the bone with which it is connected will fracture before the 

 fibrous tissue will give way. When examined under the microscope it is found to 

 consist of waving bands or bundles of minute, transparent, homogeneous filaments 

 or fibrillne, held together by an albuminous semi-fluid cement-substance (Fig. 14). 

 In ligaments and tendons these bundles run parallel with each other ; in mem- 

 branes they intersect one another in different places. The bundles have a 

 tendency to split up longitudinally or send off slips to join other bundles and 

 receive others in return. The cells occurring in white fibrous tissue are often 

 called "tendon cells." They are situated on the surface of groups of bundles 

 and are quadrangular in shape, arranged in rows in single file, each cell being 

 separated from its neighbors by a narrow line of cement-substance. The nucleus 

 is generally situated at one end of the cell, the nucleus of the adjoining cell being 

 in close proximity to it (Fig. 15). Upon the addition of acetic acid to white 

 fibrous tissue it swells up into a glassy-looking, indistinguishable mass. When 

 boiled in water it is converted almost completely into gelatin. 



Yellow Elastic Tissue. In certain parts of the body a tissue is found which 

 when viewed in mass is of a yellowish color, and is possessed of great elasticity, so 

 that it is capable of considerable extension, and when the extending force is with- 

 drawn returns at once to its original condition. This is yellow elastic tissue, in 



FIG. 13. White fibrous tissue. High power. 



