48 PROTOPLASM. 



On tJie Production of Formed Material. 



The processes of growth and increase, as they occur in 

 the tissues of all fully-formed living beings, may be well 

 studied in the simple tissue which forms the external cover- 

 ing of the body, and is prolonged in a modified form into 

 the internal cavities. If a thin section be made perpendi- 

 cularly through this, down to the tissue which contains the 

 nerves and blood-vessels upon which it rests, the appear- 

 ances represented in pi. IV, fig. 12 will be observed. 



In the first place, it will be remarked that in equal bulks 

 of the tissue there is a larger quantity of germinal matter in 

 the lower part, a, which is close to the vessels, than in the 

 upper part, <r, which is a long distance from the nutrient 

 surface, and that the converse is the case as regards the 

 formed material which gives to this tissue its properties 

 and physical characters. Secondly, it will be noticed that 

 the individual masses of germinal matter increase in size 

 till they arrive at about half way towards the surface, ^, while 

 from this point to the surface they diminish, c ; and thirdly, 

 that the distance between them increases on account of the 

 increased formation and accumulation of formed material. 

 By the time the cells have reached the surface, the distance 

 between the masses of germinal matter is reduced again, by 

 the drying and condensation of the formed material. 



The changes which each individual cell or anatomical 

 unit passes through may now be considered. At the deep 

 aspect near the nutrient surface are masses of germinal matter 

 embedded in a soft, mucus-like, and, as yet, continuous 



