INTRODUCTORY ADDRESS. 
619 
plays the same part in the animal economy in the produc- 
tion of heat, as sugar and starch do in the like process 
during the germination and budding of plants. The obser- 
vations on the power of the pancreatic juice in reducing 
fatty matters, are in the same line of investigation. . 
The French and German chemists have, of late years, en- 
tered on a common path of analysis and inquiry, which tends 
towards the gradual revelation of the secrets of a chemical 
pathology. . . . All the forces of the several structures 
of the body are dependent upon their chemical constitution, 
and on that of the health of the fluids, by which their health 
and power are sustained. Each vital organ is an apparatus, 
in which the chemical laws and atomic constitution of its 
parts are instruments, operating under the new conditions 
of life, for objects which each distinct animal or vegetable is 
intended to accomplish. If any tissue, or any fluid feeding a 
tissue, degenerate, the phenomena of life are disturbed. If 
we had the analytic power needed for the definition, we 
should find that chemical changes occur in every disease, 
both in the solid structures and humours of the body.” I 
adduce these facts to show you the bearing of chemistry on 
your studies, for the artificial formation of organic com- 
pounds is at the present time a favorite pursuit with 
chemists. 
Another circumstance that very remarkably influences the 
chemical properties of some bodies, without in the least 
changing their nature, the cause being supposed to be de- 
pendent upon an altered molecular arrangement, is allo- 
trophy. The most remarkable substances thus affected 
are, perhaps, oxygen, carbon, sulphur, and phosphorus. The 
last-named is capable of existing in no less than five forms, 
each possessing its characteristic properties. If it be heated 
to a temperature of about 44°, it becomes altogether changed 
in its characters. It may be handled with impunity, is of a 
dark-red colour, and not inflammable. If, however, it be 
now heated a hundred degrees higher it melts, and again as- 
sumes the appearance and properties of ordinary phosphorus. 
The singular substance, ozone , is proved to be an allotropic 
form of oxygen. There appear to be strong reasons for be- 
lieving that many of the nitrogenized organic bodies which 
constitute so large a portion of the food and tissues of ani- 
mals, are only allotropic forms of one and the same sub- 
stance, since chemistry has not been able to detect the 
slightest difference in their composition. The student, 
therefore, must not think that science merely enlarges and 
complicates that which is known — increasing the number 
