440 MAMMALIA— PHYSIOLOGY 



the iron in blood, oxygen could not be carried to the tissues. Iron is 

 requisite to oxidative processes and is contained in hemoglobin. 

 With an ample supply of calcium^ the body needs less iron. Lack 

 of iron leads to insufficient nutrition, anemia, and death. Certain 

 wave-lengths of ultra-violet light increase the blood content of iron. 

 Although not a constituent of the chlorophyll molecule, iron acts 

 as a catalyzer in the production of chlorophyll. Millikan has said, 

 " From an engineering standpoint, the universe may be said to be 

 made up of the primordial positive and negative electrons, and of 

 four elements built out of them; namely, helium, oxygen, silicon, 

 and iron." 



Manganese. — Lindow and Peterson have presented data (1927) 

 on the manganese content of eighty-four materials, covering the 

 principal classes of human foods. Pineapples, beet-tops and blue- 

 berries contained relatively large amounts (122-134 mgm.). Hog 

 liver contained 12.2 mg. per kilogram of dry material while beef 

 spleen and round steak contained none. The liver of young animals 

 is the storehouse for the body's reserve of manganese and other 

 mineral elements apparently necessary for the maintenance of 

 physiological equilibrium. The human body contains only one- 

 half ounce of manganese, but a deficiency results in disease. McCar- 

 rison reports (Ind. Jour. Med. Res., vol. 14, p. 641) that daily doses 

 of manganese chloride, 0.0327 mgm., caused accelerated growth in 

 rats, especially marked in the males. Manganese is said to increase 

 in amount as plants grow older. 



Bromine^ boron^ zinc, and aluminium are present in small quanti- 

 ties in plants and are important to the life and growth of the plant. 

 Their exact significance as food for the living animal is not fully 

 understood. Bradley (1904) found zinc in the blood of the gastro- 

 pod Sycotypus {Fulgur) canaliculatus. 



Enzymes are produced in living cells, some of which, the glands, 

 are specially modified to produce important bodily secretions (pan- 

 creatic juice). Enzymes are able as catalysts to hasten chemical 

 reactions, but do not form a part of the end products of the reaction. 

 An example of catalysis to which we have already referred (page 

 436) is that of iron which in the presence of light hastens the com- 

 bination of hydrogen and oxygen to form water. The genes are 

 said to act as auto-catalysts in that they increase their own sub- 

 stance prior to each mitosis. (See page 500.) 



