42 THE POPULAR SCIENCE MONTHLY. 



of the human intellect, and by the instrumentality of physical foi-ces, 

 be formed artificially at will. 



l!i 1828, Wohler, a German chemist, discovered that cyanate of 

 ammonia, a purely mineral compound, under certain circumstances 

 became changed into urea, without either loss or gain of any foreign 

 body, the elements rearranging themselves to form a more complex 

 structure. But here it was claimed, by the vitalists, that urea, being 

 an excrementitious substance, and one of the waste products of the 

 animal system, must be considered as in reality a mineral, and only 

 accidentally, as it were, akin to animal tissue. 



There exists in the bodies of ants a secretion which apparently 

 serves them as a weapon ; it is called formic acid, and, for some years 

 after its discovery, was universally prepared by pounding up sundry 

 ounces of ants in a mortar, and distilling them with water, when the 

 bodies of the insects were left in the retort, and a diluted acid, was 

 found in the receiver. Analysis showed this substance to be formed 

 of but three elements, and which, moreover, did not appear to be united 

 in a complex manner. From certain analogies it was inferred that 

 the acid might be obtained by some method of gradual oxidation ; at 

 last, the right substance was found, and, by duly acting on starch by 

 oxygen, formic acid was produced. This was considered a very great 

 step in advance, for an animal product had been at last formed from 

 a vegetable one ; and though it is true the body in question had a sim- 

 pler constitution than the starch, still the plane of possible chemical 

 processes had been elevated into the animal kingdom. 



Quite recently a method has been discovered by which formic 

 acid may be generated directly from its elements. To do this, carbon, 

 say a bit of charcoal or coke, is heated in a limited supply of air, and 

 the result is carbonic oxide ; this gas, if exposed for a long time over 

 caustic potash, combines with it, and this product, if distilled with oil 

 of vitriol, yields formic acid. Thus the body has been formed with- 

 out any thing having been used which is the product of life. 



From this point progress was rapid, though at first apparently 

 it rather tended away from the matter at issue. Previous study in the 

 department of mineral chemistry had gradually forced the conception 

 that the position of the elements in a compound had as much to do 

 with its properties as did their number and amount, and it also had de- 

 veloped the fact that certain elements might be withdrawn and their 

 places filled by something else, without changing the general character 

 of the substance. Indeed, a compound body was called a chemical 

 structure, and likened to a real edifice, in which the elementary atoms 

 were the bricks of the house, and the resulting properties constituted 

 the shape of the building. Now, by replacing one element by another, 

 the same kind of change was produced as would be caused by the 

 substitution of marble for bricks, or iron for stone, in the real house. 

 Its appearance and habitability might be greatly altered, but its gen- 

 eral shape and character remained. 



