118 VEGETABLE PAEASITES. 



being able to prove it with certainty (we need only think of the 

 cholera-parasites, which proved to be quite chimerical), epidemic 

 diseases have, from time to time, been accounted for as produced by 

 certain microscopic vegetable parasites. Robin is quite right, when 

 he says " This whole hypothesis is merely an attempt of medical 

 men to seek the external conditions of the existence of universal 

 affections in the changes of the internal constitution of beings, 

 their atoms and molecules. Should there really be such vege- 

 table parasites discovered in epidemic diseases, they might rather 

 pass for consequences of the epidemic disorder of the fluids which 

 has set in, than for the causes of such epidemics/' It is, un- 

 fortunately, not yet quite clear what disorder of the fluids is 

 necessary to make a single parasite thrive well. The disputed 

 question, when better decided than it is now, as to whether cer- 

 tain vegetable parasites, when transferred to any organism (no 

 matter whether healthy or diseased), can develop themselves 

 well, or whether they thrive only on special organisms, will 

 enable us to decide the first question with greater certainty. 

 All observations are yet incomplete; and we entirely lack ele- 

 mentary observations on the temperature and degree of humidity 

 of the atmosphere, which are certainly of no little influence, 

 during some seasons or years, with regard to the more frequent, 

 almost epidemic appearance of certain vegetable parasites. 



Literature. Principal work, ' Histoire naturelle des vegetaux 

 Parasites qui croissent sur 1'homme et sur les animaux vivants/ 

 par Charles Robin (avec un Atlas), Paris, 1853. 



