12. _The distinction between plants and animals_ is also of much importance. _Animals grow proportionally in all directions_, while plants grow upwards and downwards from a collet only. The _food_ of animals is _organic_, while that of plants is _inorganic_; the latter feeding entirely upon the elements of the soil and atmosphere, while the former subsist upon the products of the animal and vegetable kingdoms. The size of the vegetable is in most cases limited only by the duration of existence, as a tree continues to put forth new branches during each period of its life, while the animal, at a certain time of life, attains the average size of its species. 13. One of the most important distinctions between animals and plants, is _the different effects of respiration_. Animals consume the oxygen of the atmosphere, and give off carbonic acid; while plants take up the carbonic acid, and restore to animals the oxygen, thus affording an admirable example of the principle of compensation in nature. 14. But the decisive distinctions between animals and plants are _sensation_ and _voluntary motion_, the power of acquiring a knowledge of external objects through the senses, and the ability to move from place to place at will. These are the characteristics which, in their fullest development in man, show intellect and reasoning powers, and thereby in a greater degree exhibit to us the wisdom and goodness of the Creator. -=-=-=-=-=-=-=-=-=-=-=-= 11. What is said of the individuality of organized and inorganized bodies? What is closely associated with this? 12. Give a distinction between animals and plants as regards growth. The food of animals and plants. What is said in respect to size? 13. What important distinction in the effects of respiration of animals and plants? 14. What are the decisive distinctions between animals and plants? -=-=-=-=-=-=-=-=-=-=-=-= 15. DISEASE, which consists in an unnatural condition of the bodily organs, is in most cases under the control of fixed laws, which we are capable of understanding and obeying. Nor do diseases come by chance; they are penalties for violating physical laws. If we carelessly cut or bruise our flesh, pain and soreness follow, to induce us to be more careful in the future; or, if we take improper food into the stomach, we are warned, perhaps immediately by a friendly pain, that we have violated an organic law. 16. Sometimes, however, the penalty does not directly follow the sin, and it requires great physiological knowledge to be able to trace the effect to its true cause. If we possess good constitutions, we are responsible for most of our sickness; and bad constitutions, or hereditary diseases, are but the results of the same great law,--the iniquities of the parents being visited on the children. In this view of the subject, how important is the study of physiology and hygiene! For how can we expect to obey laws which we do not understand? -=-=-=-=-=-=-=-=-=-=-=-=