SEVENTEENTH AND EIGHTEENTH CENTURIES 157 



and less experimental than the latter's, and therefore, though published 

 earlier, it has not the same universal application as the work De motu animal- 



ium. 



Steno as a paleontologist 

 Besides the above work Steno found time during the short period which he 

 devoted to natural science to make a number of important contributions. 

 Thus, he discovered the ovaries in the shark, which, as is well known, 

 produces its young alive — a discovery the importance of which he himself 

 fully realized; up to that time people had thought that ovaries existed only 

 in oviparous animals. Steno's greatest service to biology, however, is his 

 creation of modern palaeontology. Already during his first visit to Florence 

 he had had an opportunity of studying a kind of stone images found in great 

 numbers there, which the inhabitants called " glossopetrf or stone-tongues, 

 and by means of comparative study he proved that they must have been the 

 teeth of sharks. During his later sojourn in Tuscany he carried out a system- 

 atic study of that district's geological strata, and thought himself justified 

 in concluding from their position and appearance that they had been strati- 

 fied out of water, a fact which he believed to be still further confirmed by 

 the quantity of animals and plants found in them. Supported by these facts, 

 he outlines a theory of the origin of the earth's strata which is a presage of 

 present-day geological science. He never got further than this rough out- 

 line, however; the results of his geological investigations would not, as 

 the times were then, accord with the Church doctrine that he had so zeal- 

 ously embraced, and, indeed, this was one of the reasons why he completely 

 abandoned a science which he had initiated and studied with such splendid 

 results. A tragic fate indeed, although by no means without its counterpart 

 in scientific history. In this his last natural-scientific work, however, Steno 

 deals also with other problems besides the purely geological and pateonto- 

 logical. His geological stratification theory is really only one link in a gen- 

 eral theory regarding transubstantiation in nature, according to which all 

 things that exist have originally been and are still being precipitated out of 

 fluids. He thus comes to the question of the crystallization process in the 

 mineral kingdom, which he investigated with great thoroughness and good 

 results, and in connexion therewith he discusses the transubstantiation and 

 organic formation in animals, which he likewise conceives to be a strati- 

 ficational process similar to that which takes place in inanimate nature, a 

 precipitation from fluids, of which he distinguishes various kinds in the ani- 

 mal and plant organism. Thus he reconciles the changes in substance in ani- 

 mate and inanimate nature under the same point of view and without giving 

 any idea of the essential diff^erence between the growth of a crystal and that 

 of a living organism. This, then, clearly denotes the limitation in the me- 

 chanical conception of nature in the seventeenth century — a limitation 



