CELLULAR TISSUE. 



497 



Fig. 232. 



spherical form, as seen in the photograph, Fig. 232. But should the 



development occur in a confined space, 

 or under circumstances of pressure, the 

 intercellular spaces which necessarily ex- 

 ist in the former case by reason of the 

 spherical shape, are now encroached upon, 

 and the cells assume various angular 

 forms, such as parallelopipedons, rhom- 

 bic dodecahedrons, &c. Of the former 

 we have an example in the photograph, 

 Fig. 233, which represents a section of 

 muriform cellular tissue. In other,cases, 

 with a view of giving resistance to press- 

 simple cellular tissue, magnified 50 diameters. ^ the i nte rior of each O f the Cells is 



fortified by a fibre, and thus arises the tissue of which we have an exam- 



Fig. 23.4. 

 Fig. 233. 



Muriform cellular tissue, magnified 50 diameters. 



Fibro-cellular tissue, magnified 50 diameters. 



pie in the photograph, Fig. 234. Two or more fibres may, in this man- 

 ner, be employed, and when such is the case, it is observed that they do 

 not cross one another, the one winding from right to left, the other from 

 left to right, but they are laid parallel to each other, and form a com- 

 pound strand. In other cases the constituent cells of the tissue assume 

 much more complicated forms, as, for instance, in the stellate variety. 

 These more complicated forms prove that it is not altogether through 

 the influence of a force of compression that cells assume modified shapes, 

 but that on many occasions the disposition of their primordial utricle to 

 branch in various directions, of which mention has been made in a pre- 

 ceding paragraph, is the true cause of the variations in question. 



This disposition to grow spontaneously in one direction rather than in 

 another is the cause of the production of the different kinds of vascular 

 tissue. A cell undergoing extreme elongation in one direction, either by 



II 



