8i 



OEXEMAL PRINCIPLES OF ZOOLOGY. 



]ir<ipiirtioii as tlio intercellular suljstance increases in volume the 

 cells themselves diminish and become inconspicuous corpuscles, 

 the connective-tissue corpuscles, or, as seldom happens, entirely 

 disappear. (Since, in the connective tissues, the intercellular sub- 

 stances are most important, it is readily nnderstood that the dis- 

 tinctions between the various kinds of connective tissue rest chiefly 

 npon the difierences of this intercellular substance. The following 

 forms are to be distinguished: (1) cellular connective tissue; (2) 

 homogeneous connective tissue; (3) fibrous connective tissue; (4) 

 cartilage; (.5) bone. 



Cellular Connective Tissue shows the characteristics of the 

 group least distinctly. It owes its name to the fact that the cells 

 make up the chief mass, while the cell-products are inconsiderable. 

 The cells are large and vesicular bodies whicli, like plant cells, are 

 closely pressed together and arc consequently polygonal (fig. 38). 

 They have secreted Ijetsveen them a firm but thin layer of inter- 

 cellular substance. 



Fig. 38. — CeUular coniu-otive substance. 

 Cross-section throut^h the notochord 

 of a newly hatched Trout. 



Fig. 39.— >Iomo^'eneous connective sub- 

 stance ot Xiiciindi-a rapluiinDi. (After 

 F. E. Schulze.) 



Homogeneous Connective Tissue — In the case of Jiomogencous 

 connective svhsUmce the ijiterccllular substance (or matrix) is 

 usually present in considerable quantity as a transparent mass, 

 nearly invisible under the microscope, sometimes soft like jellv. 

 often firmer (fig. 3i)). ^I'he gelatinous cells lying in it are either 

 splierical or send Ijranehing processes into the matrix. Such 

 processes may unite to form meslies which, like a pseudopodial 

 network, unite cell to cell. Frequently the matrix contains, in 

 addition, isolated firm filires or threads, which, on account of 



