STRUCTURAL COMPOSITION OF THE BODY. 15 



These principles, which represent waste, are of organic origin, arising 

 within the body as products of disassimilation or retrograde metamorphosis 

 of the tissues; they are absorbed by the blood, carried to the various 

 excretory organs, and by them eliminated from the body. 



The excrementitious substances will be fully considered under excretion. 



Proximate Quantity of the Chemical Elements and Proximate 



Principles of the Body, Weighing 154 Ibs. 



Ibs. oz. Ibs. oz. 



Oxygen in ... Water in ... 



Hydrogen 14 ... Albuminoids 23 7 



Nitrogen 3 8 Fats 12 ... 



Carbon 21 ... Calcium phosphate 5 13 



Calcium 2 .*.. Calcium carbonate I 



Phosphorus I 12 Calcium fluoride 3 



Sodium, etc 12 Sodium sulphate, etc 9 



154 ... 154 ... 



STRUCTURAL COMPOSITION of THE BODY. 



The Study of the Structure of the body reveals that it is composed 

 of dissimilar parts, e. g., bones, muscles, nerves, lungs, etc.; while these, 

 again, by closer examination, can be resolved into elementary structures, 

 the tissues, e.g., connective tissue, muscular, nervous, epithelial tissue, etc. 



Microscopical examination of the tissue shows that they are com- 

 posed of fundamental structural elements, termed cells. 



Cells are living physiological units ; the simplest structural forms capable 

 of manifesting the phenomena of life. 



Cells vary in their anatomical constitution in the different structures ot 

 the body, and may be classed in three groups, viz.: i. Cells possessing a 

 distinct cell wall, cell substance and a nucleus. 2. Cells possessing a cell 

 substance and a nucleus. 3. Cells possessing the cell substance only. 

 They vary in size, from the jfoy to the J- 7 of an inch in diameter ; when 

 young and free to move in a fluid medium they assume the spherical form; 

 but when subjected to pressure, may become flattened, cylindrical, fusiform 

 or stellate. 



Structure of Cells. The cell wall is not an essential structure, as 

 many cells are entirely devoid of it. It is a thin, structureless, transparent 

 membrane, permeable to fluids. 



The Cell Substance in young cells is a soft, viscid, albuminous matter, 



