42 report — 1842. 



Abstract of Professor Liebig's Report on " Organic Chemistry ap- 

 plied to Physiology and Pathology. By Lyon Playfair, M.D. 



The first part of Professor Liebig's Report consists in the examination of 

 the processes employed in the nutrition and reproduction of various parts of 

 the animal ceconomy. 



In vegetables, as well as in animals, we recognise 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 the presence of air and moisture, its condition of static equilibrium is dis- 

 turbed ; and entering into a state of motion or activity, it occupies itself 

 in the production of forms, which, though occasionally bounded by right 

 lines, are yet widely distinct from geometrical forms. This force has re- 

 ceived the appellation of vital force, or vitality. 



Vitality, though residing equally in the animal and vegetable kingdoms, 

 produces its effects by widely different instruments. Plants subsist entirely 

 upon matter belonging to inorganic nature. Atmospheric air, the source 

 whence they derive their nutriment, is ranked with minerals 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 organised atoms for nutri- 

 ment ; they can only subsist upon parts of an organism. They possess within 

 themselves 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 nervous apparatus. The true vegetative life of animals is in no 

 way dependent upon this apparatus ; for it proceeds where the nerves of vo- 

 luntary motion and sensation are destroyed, and the most energetic volition 

 is incapable of exerting any influence on the contractions of the heart, on the 

 motion of the intestines, or on the processes of secretion. 



All parts of the animal body are produced from the fluid circulating within 

 its organism, by virtue of vitality, which resides in every organ. A destruc- 

 tion of the animal body is constantly proceeding ; every motion, every mani- 

 festation of force, is the result of the transformation of the structure, or of its 

 substance ; every conception, every mental affection, is followed by changes 

 in the chemical nature of the secreted fluids ; every thought, every sensation, 

 is accompanied by a change in the composition of the substance of the brain. 



It is to supply the waste thus produced, that food is necessary. Food is 

 either applied in the increase of the mass of a structure (i. e. in nutrition), or 

 it is applied in the replacement of a structure wasted (i. e. in reproduction). 



The primary condition for the existence of life is the reception and assimi- 

 lation of food. But there is another condition equally important — the con- 

 tinual absorption of oxygen from the atmosphere. 



All vital activity results from the mutual action of the oxygen of the at- 

 mosphere and the elements of the food. All changes in matter proceeding 

 in the body are essentially chemical, although they are not unfrequently in- 

 creased or diminished in intensity by the vital force. The influence of poi- 

 sons and remedial agents on the animal ceconomy, proves that the chemical 

 combinations and decompositions proceeding therein, and which manifest 

 themselves in the phaenomena of vitality, may be influenced by bodies pos- 

 sessing a well-defined chemical action. Vitality is the ruling agent by which 

 the chemical powers are made to subserve its purposes, but the acting forces 

 are chemical. It is from this view, and from no other, that we ought to view 

 vitality. Wonders surround us on all sides : the formation of a crystal is not 



