Volume 1
A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling.
- Landois, L. (Leonard), 1837-1902. Lehrbuch der Physiologie des Menschen. English
- Date:
- 1891
Licence: Public Domain Mark
Credit: A text-book of human physiology : including histology and microscopical anatomy with special reference to the requirements of practical medicine / by L. Landois ; translated from the seventh German edition with additions by William Stirling. Source: Wellcome Collection.
39/602 page 35
![The Proteids contain per cent. :— I C. 51-5-54-5 ] H. 6-9- 7-3 N. 15-2-17-0 0. 20-6-23-5 S. 0-3- 2-0 (§§ 248 and 249). A man who takes a certain amonnt of this food adds thereto oxygen from the air in the process of respiration. Combustion or oxidation then takes place, where- hj chemically-potential energy is transformed into heat. It is evident that the products of this combustion must be bodies of simpler con- stitution—bodies with less complex arrangement of their atoms, with the greatest possible saturation of the affinities of their atoms, of greater stability, partly rich in 0, and possessing either no potential energy, or only very little. These bodies are carbon dioxide, CO^; water, HgO ; and as the chief representative of the nitrogen- ous excreta, urea (CO(N'H2)2), which has still a small amount of pottential energy, but which outside the body is readily converted into CO^ and ammonia (NHg). The human body is an organism in which, by the phenomena of oxidation, the complex nutritive materials of the vegetable kingdom, which are highly charged with potential energy, are transformed into simple chemical bodies, whereby the potential energy is transformed into the equivalent amount of kinetic energy (heat, work, electrical phenomena). But how do plants form these complex food-stu£fs so rich in potential energy ? It is plain that the potential energy of plants must be obtained from some other form of energy. This potential energy is supplied to plants by the rays of the sun, whose chemical light-rays are absorbed by plants. Without the rays of the sun there could be no plants. Plants absorb from the air and the soil C02,Tl20, N'Hg, and E, of which carbon dioxide, water, and ammonia (from urea) are also produced by the excreta of animals. Plants absorb the Idnetic energy of lujld from the suit's rays and transform it into potential energy^ which is accumulated during the growth of the plant in its tissues, and in the food-stuffs produced in them during their growth. This formation of complex chemical compounds is accom- panied by the simultaneous excretion of 0. Occasionally, kinetic energy, such as we universally meet with in animals, is liberated in plants. Many plants develop considerable quantities of lieat in their flowers, e.g., the arum tribe. We must also remember that during the formation of the solid parts of plants, when fluid juices are changed into solid masses, heat is set free. In plants, under certain circum- stances, 0 is absorbed, and COg is excreted, but these processes are so trivial as compared with the tj'pical condition in the vegetable kingdom, that they may be regarded as of small moment. Plants, therefore, are organisms which, by a reduction process, transform simple stable combinations into complex compounds, whereby potential solar energy is transformed into the chemically-potential energy of vegetable tissues. Animals are living beings, which by oxidation decompose or break up the complex grouping of atoms manufactured by plants, whereby potential is transformed into kinetic energy. Thus, there is a constant circulation of matter and a constant exchange of energy between plants and animals. All the energy of animals is derived from plants. All the energy of plants arises from the sun. Thus the sun is the cause, the original source of all energy in the organism, i.e., of the whole of life.](https://iiif.wellcomecollection.org/image/b20417688_001_0039.jp2/full/800%2C/0/default.jpg)
