TUMORS. 



527 



stance surrounds fully developed epithelia. The difference is that the spin- 

 dles are homogeneous and shining, of the same refracting power as the 

 granules and threads of living matter, while the cement-substance is a pale 

 layer without any refracting power. Evidently, the spindles are compact 

 masses of living matter from which future epithelia arise, while the cement- 

 substance proper is a lifeless, horny material, containing only very little liv- 

 ing matter in the shape of the minute thorns that traverse it. 



Where there is no sharp demarcation between connective tissue and epi- 

 thelium, even the highest powers of the microscope fail to demonstrate where 

 one terminates and the other begins. Only the presence of capillary blood- 



FIG. 218. PAPILLA, WITH SURROUNDING EPITHELIUM. 

 OBLIQUE SECTION. 



a, bundle of fibrous connective tissue ; &, plastid between the spindles ; c, myxomatous 

 connective tissue ; d, capillary blood-vessel cut across ; e, layer of connective tissue at the 

 base of the epithelia; /, spindle-shaped prolongations of the layer e, insinuated between 

 the epithelia; g, columnar epithelium; li, medullary tissue, transition of connective tissue 

 into epithelium. Magnified 1200 diameters. 



vessels furnishes some guidance for the determination of what is connective 

 tissue. (See Fig. 218.) 



In the lower strata of epithelia we most frequently meet with the 

 appearances in the cement-substance already described. The high power 



