PROCEEDINGS OF THE POLYTECHNIC ASSOCIATION. 521 



from compounds that no animals have had anything to do with. 

 For instance, the acid matter of sour-krout is lactic acid — tho 

 same that is found in sour milk. 



Another interesting fact is that the organic compounds can be 

 so readily arranged in well defined classes. For example, there 

 are a dozen of the petroleum or coal oils so similar to each other 

 that any child can see that they ought to be classed together. One 

 differs from another principally in being more or less volatile. 

 And so with any organic substance, it may be classed with hun- 

 dreds, perhaps, of others, resembling it, or connected with it. 



Mr, C. W. Smith. — One of the. first things that will be observed 

 by the student of organic chemistry, is the tendency to form 

 series. Taking a certain compound, we find that adding a defi- 

 nite quantity of perhaps two elements, we produce another com- 

 pound, and so we can go on and build up a series, proceeding step 

 by step, to the extent, in some cases, of forty or fifty different com- 

 pounds, varying from each other by precisely the same differen- 

 tial. This is something entirely different from anything we meet 

 with in inorganic chemistry. The tendency of discovery is to in- 

 crease the number and extent of these series. We commence 

 with a substance highly volatile, and by adding C2 H2, or what- 

 ever the increment may be, we build up a series of substances 

 less and less volatile, until perhaps at last we reach a solid, or 

 at least a substance nearly solid. 



Prof Joy, being called upon, said that the series of homologous 

 substances, commencing with C2 H2 O4, C4 H4 O4, Ce He O4, up 

 to C36 H36 O4, was now nearly complete. Such series have led to 

 the idea that iodine, bromine, etc., may be compounds differing 

 by some homologue which we have not yet discovered. The old 

 idea of transmuting all metals into gold is founded upon a similar 

 notion, for if we could find a common difference between the 

 metals, we should merely have to add or to subtract this common 

 diflference in order to convert one into another. 



The growth of plants, by the formation of little globules or 

 cells, building up one upon another, is like the building of a 

 house with bricks. The plants begin with very small cells, which 

 have the power, not understood as yet, of taking up carbon, 

 hydrogen, oxygen and nitrogen, in the necessary proportions ; 

 and as each cell is formed another is built upon it, and So on. 

 The chemist can furnish the nourishment, but the vital power is 

 the great mystery. It is something we cannot imitate ; and it is 



