CELLULAR DIFFERENTIATION. 5 3 



77. Nutritive Fluids. The body fluids known as blood and lymph are 

 frequently classed among the supporting tissues, the fluid portion being 

 regarded as the intercellular substance and the corpuscles as the cells. 



FIG. 25. Blood corpuscles (amphibian), c, colored corpuscles, flatwise and in profile; 

 /, colorless corpuscles (.leucocytes). 



FIG. 26. 



FIG. 26. 



Blood corpuscles (human), c, colored; /, leucocytes. The red cells tend to 

 collect in rows with the sides in contact. 



Questions on figures 25 and 26. Compare by means of the figures, 

 the text and reference books the colored and colorless corpuscles of 

 these two types of vertebrates and note the differences. In what other 

 respects do the colored cells differ from the white? Which are the less 

 highly differentiated? Reasons for your view? Why are the colorless 

 corpuscles also called phagocytes? 



They differ however from the ordinary tissues in the important fact that 

 the intercellular substance is not produced by the cells. In the vertebrates 

 these cells are of two kinds, the amoeboid or colorless and the colored. 

 Both kinds occur in the blood ; the colorless alone are found in the lymph. 

 The colored corpuscles are relatively numerous and are disc shaped. Re- 

 garded as cells they present a series of degenerative changes which results 

 in a loss of the distinctively protoplasmic character, by the substitution 



