STRUCTURAL COMPOSITION OF THE BODY. 17 



Proximate Quantity of the Chemical Elements and Proximate 

 Principles of the Body, Weighing 154 Ibs. 



Ibs. 07.. 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 tissues 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 of 

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

 distinct cell wall, cell stibstance 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 g^Vtf to the ^00 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, 

 unstable, insoluble in water, and known as protoplasm, bioplasm, sarcode, 

 etc. ; in older cells the original cell substance undergoes various transform- 

 ations, and is partly replaced by fat globules, pigment and crystals. 



The Nucleus is a small vesicular body in the interior of the cell sub- 

 stance, and frequently contains smaller bodies, the nucleoli. 



