64 ORIGIN OF THE TISSUES. 



It arises, as is supposed, by the blending together of the 

 granules about a central point, as they are being deposited 

 from the amorphous mass their common birth-place and 

 origin. 



This mode of origin and development has been observed 

 in the egg of animals and germ of plants. 



The Nucleated Cell, thus formed, multiplies in number, 

 and blends and coalesces with the newly formed cells, and 

 by various metamorphoses ultimately forms all the different 

 tissues of which the body is composed. 



The cells increase, either by the origin of new ones, singly 

 and independently the one of the other or by the pri- 

 mary cell developing within itself a series of new secondary 

 Cells, which, in their turn, give origin to others, and so 

 on, successively. 



The Hair, Nails, and inflammatory exudation, are cited 

 as examples of the first mode of increase and the Liver, 

 and pathological growths, as scirrhus, as specimens of the 

 second. 



The Cells, as they are passing through their various 

 stages of development, to the formation of the different 

 tissues, necessarily change their shape, position, contents, 

 and relations; as, for instance, in some Tissues they pre- 

 serve their independence, and, by being situated the one 

 upon the other, become thereby flattened, or pointed and 

 elongated: others increase in size, as the fat Cells, or di- 

 minish in size, as the lymph corpuscles when changed into 

 blood corpuscles; or lose their Nucleus, as in the mature 

 blood-corpuscle; or have their parietes thickened, as the 

 Cartilage Cells. 



The Cells, in most of the Tissues, come together and coa- 

 lesce. By this process the cavities of the Cells present two 

 conditions; in the one case they remain open, in the other 

 they disappear. 



Examples of the remaining Cell cavity are seen in true 

 Cartilage and Osseous Tissue, where the thickened cell walls 

 are blended together, or their parietes, in contact with one 



