PART I 



GENERAL PHYSIOLOGY AND MORPHOLOGY 



A. CHEMICAL AND PHYSICAL CHARACTERISTICS OF 



LIVING THINGS. 



The bodies of all living things are composed of about 15 chemical 

 elements and a great number of chemical compounds : 97 per cent 

 of the human body consists of carbon, hydrogen, oxygen and nitro- 

 gen, and 3 per cent of n other elements. Three-fourths of all the 

 hydrogen and nine-tenths of all the oxygen are combined to form 

 water. In addition to water and mineral salts living things con- 

 tain carbon compounds, or "organic compounds." Compounds of 

 carbon, hydrogen and oxygen form Carbohydrates or Hydrocarbons ; 

 compounds of carbon, hydrogen, oxygen and nitrogen form Protcids. 



I. CARBOHYDRATES (Starches, Sugars). 



Carbohydrates of physiological importance are :- 



Polysaccharids ( C t; H 1(l O- ) u -starch, dextrin. 

 Monosaccharids (C H 12 O 6 ) dextrose. 

 Disaccharids (C 12 H 22 O ll ) cane sugar. 



i. a. POLYSACCHARIDS. Native starch. Mount a scraping of 

 potato in water and examine under microscope. Study and draw 

 structure of starch grains. Run a drop of iodine solution under 

 cover. What happens ? 



b. Grind a little commercial starch in a mortar and shake with 

 cold water. Filter and test filtrate with iodine. 



c. Test solubility in boiling water. Note character of resulting 

 solution. Dilute and add a drop or two of iodine solution. What 

 results? Heat and cool again noting result. Add (i) alkali, (2) 

 alcohol to the colored solution. What results ? 



d. Cellulose (plant cell-walls). Cotton fiber is almost pure cel- 

 lulose. Note insolubility in water and alcohol. Is it insoluble in 

 acids? Alkalies? Does it react with iodine? Treat with 20 per 

 cent sulphuric acid and then add iodine. What results ? Treat with 

 Schultze's chlor-zinc-iodide. What results ? This is known as the 

 "cellulose test." 



