558 Proceedings of the British Association. 



the same number were always to be found, so long as the velocity 

 remained unchanged. 



THURSDAY. 



Section B. — CHEMISTRY AND MINERALOGY. 



The venerable President sat on the right hand of the chair, and 

 left the active duties of the office to Prof. Graham. 



Dr. Playfair read an abstract of Prof. Liebig's Report on Organic 

 Chemistry, applied to Physiology and Pathology. 



Dr. Playfair said, that Prof. Liebig had been requested, some few 

 years ago, to apply himself to the consideration of questions in vegeta- 

 ble and animal physiology. The Professor's first Report had been read 

 at the meeting of the Association at Glasgow, in the year 1840. 

 The second he was about to bring before their notice. And in a third, 

 the Professor intended to apply the principles of organic chemistry 

 to diet and dietetics ; and under this head would be comprised the nu- 

 tritiveness of particular vegetables in the fattening of cattle. The first 

 part of Prof. Liebig's Report consisted of the examination of the 

 processes employed in the nutrition and reproduction of the various 

 parts of the animal economy. In vegetables, as well as in animals, we 

 recognize the existence of a force in a state of rest. It is the primary 

 cause of growth or increase in mass of the body, in which it resides. 

 By the action of external influences, such as by pressure of air and 

 moisture, its condition of static equilibrium is disturbed; and enter- 

 ing into a state of motion or activity, it occupies itself in the pro- 

 duction of forms. This force has received the appellation of vital force 

 or vitality. Vitality, though residing equally in the animal ancUvegeta- 

 ble kingdoms, produces its effects by widely different instruments. 

 Plants subsist entirely upon manures belonging to inorganic nature. 

 Atmospheric air, the source whence they derive their nutriment, is 

 considered to be a mineral by the most distinguished mineralogists. 

 All substances, before they can form food for plants, must be resolved 

 into inorganic matter. But animals, on the other hand, require highly 

 organized atoms for nutriment. They can only subsist upon parts 

 of an organism. They possess within them a vegetative life, as plants 

 do, by means of which they increase in size, without consciousness 

 on their part; but they are distinguished from vegetables, by their 

 faculties of locomotion and sensation — faculties acting through a ner- 

 vous apparatus. The true vegetative life of animals is in no way depen- 

 dent upon this apparatus, for it proceeds when the means of voluntary 



