26 ANIMALS AND PLANTS. 



Fats contain- { Cn H > (OH) == fatt ^ adds ^ 

 1 + C 3 H 5 (OH),= glycerin J 



( C 7 6. 5 

 Animal fats contain : H 12.0 



(. O 11.5 

 Carbohydrates contain: C 6 H 10 O 5 



p 



^50-55 

 H e .e- 7 .3 



Proteids contain in percentages : N 15 _ 19 



19 - 24 

 0.3-2.4 



Man, who partakes of a certain amount of these nutrient materials, 

 adds to them through the respiratory process the oxygen of the air, 

 whence there results a process of combustion, in the course of which 

 chemical potential energy is converted into heat. It is evident that 

 the products of this combustion must be bodies of simple constitution, 

 bodies with uniform arrangement of their atoms, with most complete 

 saturation of the affinities of their atoms, of great constancy, partly 

 rich in oxygen and possessing slight or no chemical potential energy. 

 These bodies are carbon dioxid (CO 2 ), water (H 2 O), and, as the most 

 important representative of the nitrogen-containing derivatives, urea 

 (CO(NH 2 ) 2 ), which, while endowed with a small measure of potential 

 energy is, outside of the body, readily transformed into CO 2 and ammonia 

 (NH 8 ). 



Thus, the animal body is an organism in which, through the inter- 

 mediation of oxidation-phenomena, the complex nutritive matters of 

 the vegetable world, representing high potential energy, are trans- 

 formed into simple chemical bodies, in the course of which the potential 

 energy is transformed into an equivalent amount of kinetic energy 

 (heat, work, electric phenomena). 



The question naturally arises, How do plants, which, as the first 

 products of creation, found for their nourishment no preexisting mate- 

 rials endowed with potential energy, and still suffer from no lack thereof 

 how do plants form the complicated nutrient matters mentioned, 

 rich in stored-up potential energy? This potential energy of vegetable 

 life must obviously have been derived from some other form of energy, 

 for it cannot be created out of nothing. This kinetic energy is furnished 

 plants through the light of the sun, whose chemical rays they absorb. 

 Without sunlight there can be no vegetable life. From the air and the 

 earth the vegetable organism obtains CO 2 , H 2 O, NH 3 , and N, of which 

 carbon dioxid, water, and ammonia (from urea) constitute also the 

 excrementitious matters of the animal body. The plant obtains from 

 the rays of the sun the kinetic energy of its light and converts it into 

 potential energy, which, as in all vegetable matter, so also in the nutrient 

 material produced, accumulates in the process of the growth of the plant. 

 This formation of complex chemical combinations takes place in asso- 

 ciation with elimination of oxygen. 



The Papillonacese, as, for instance, peas, beans, lupines, acacias, are capable 

 of assimilating the free nitrogen of the air in the tissues of their root-bulbs, through 

 the agency of symbiotic micro-organisms lodged upon these, Rhizobium legumino- 

 sarum. Thus, these plants are capable of building up their nitrogen-containing 

 tissues even in soil entirely free from nitrogen. In this way they play an im- 

 portant fertilizing role in agriculture (lupine) and forestry (acacia). Also lower 



