286 MICROBES, FERMENTS, AND MOULDS. 



only an hypothesis, let us compare it with other hypo- 

 theses which have been proposed to explain the 

 virulent and contagious nature of certain diseases. 

 This comparison may throw some light on the question 

 at issue. 



The value of an hypothesis must be estimated by 

 the number and importance of the facts of which it 

 affords a clear, precise, and really scientific explanation ; 

 it must also be estimated by its influence on the 

 a Ivance of science. We will therefore enumerate the 

 principal theories which have been proposed to explain 

 the origin of virulent and contagious diseases, without 

 the intervention of microbes. 



Robins Theory of Blastema. Although, as far as 

 we are aware, Robin has not recently published any- 

 thing with reference to his opinion of the value of the 

 microbian theory, some of his pupils have set forth the 

 theory of blastema as it was stated by their master in 

 books published from ten to twenty years ago. 



In Robin's opinion, no cell is born from another 

 cell, in the form of a bud, an egg, or a spore. Un- 

 doubtedly there is no spontaneous generation, at the 

 expense of elements of exclusively inorganic origin ; 

 but this generation or genesis occurs every day at the 

 expense of an organized substance which is living, 

 but fluid and amorphous, and which has its source 

 from other pie-existent cells. This fluid is termed 

 blastema by Robin. Blastema is the surplus of the 

 nutritive substance, organized by the cells aud.exuded 



