4 ZOOLOGY. 



71. Cellular or Vesicular Tissue forms an exception to the general 

 rule of abundant intercellular substance. It is an embryonic tissue, a 

 forerunner of the more permanent tissues, and is chiefly interesting from 

 that fact. The cells have large vacuoles or vesicles which are enveloped 

 by a thin layer of protoplasm (Fig. 20). It is found in the notochord 

 of vertebrates. 



72. Gelatinous tissue has a matrix of intercellular substance envelop- 

 ing stellate cells, the radiating projections of which serve to connect them 

 Fibres are often developed in the matrix. This tissue is abundantly found 

 in the jelly-fish (see Fig. 21). 



73. Fibrous connective tissue has in its ground substance a rich supply 

 of fibrils variously arranged. The cells or corpuscles are often elongated 

 and branched. If the intercellular fibres cross, running in various direc- 

 tions, a loose yielding tissue results, as in the ordinary connective tissue 

 about the muscles and nerves (Fig 22, A) ; if the fibres are parallel the 

 tissue naturally becomes more compact. There are two types of the more 

 compact sort differing in the quality of the fibres. The latter may be white 

 and inelastic, as in tendons, or yellow and elastic. Fat is frequently de- 

 posited as spherical drops of oil (Fig. 22, 5) in the cells of connective 



tissue.- 



FIG. 22. 



A 



Questions on the figure. In these two types of tissue which element 

 gives special character to the tissue, the cells or the intercellular substance ? 

 How would the deposition of large drops of oil in the cell affect the activity 

 of the cell? Why? Why are fatty deposits less hurtful amid connective 

 tissue than elsewhere in the body? 



74. Cartilage. In cartilage the intercellular matrix is much firmer 

 than in those tissues already described. It may appear homogeneous as 

 in rib cartilage (Fig. 23, A) ; or it may contain numerous fibres which give 

 coherence and elasticity. The cells are usually rounded except where they 

 have been flattened by mutual pressure, and usually occur in pockets in 



