the Origin of Intestinal it^orms, 319 



superficial explanations of difficult matters, but upon carefully 

 acquired facts and laborious investigation. 



Sect. 3. Had but little credit in England. — If we consult the 

 English philosophers and physiologists of the period before the 

 last ten years, we find the question slightly treated, if not 

 passed over in silence. Dr Fleming, in vol. 1st of his Philo- 

 sophy of Zoology, Edinburgh 1822, asserts, that it is " not at 

 all difficult to give an explanation of the appearances on which 

 the whole fabric of the theory of equivocal generation rests." 

 But afterwards (p. 25) he only tells us, that "the most rational 

 explanation which can be given of the appearances of these 

 plants and animals, in such places, is derived from the consi- 

 deration of the smallness of their seeds and eggs, which may 

 be carried about by the winds, and showered down along with 

 the rains, so as to enter with facility into every situation." 



Now, if this explanation be the most rational, as it seems 

 to be, still it is nothing more than an hypothesis founded on 

 no direct observation. As to the ova being carried about by 

 the winds, it is true that the atmosphere contains organic mat- 

 ter, evaporated from living and dead organic bodies, and mi- 

 nute dried organic particles, but no instance is known of eggs 

 or seeds having been observed with the microscope in these 

 evaporations or minute particles ; although the recent obser- 

 vations of Professor Schultze, at Griefswald, have proved that 

 certain small animals, if dried to dust, may retain their vitality 

 for at least seven years. Be this, however, as it may, it is 

 highly improbable that the occurrence should have happened 

 in all or in any of the experiments which were carefully insti- 

 tuted on this subject. Rain-water might be supposed to con- 

 tain microscopic animals and plants, or at least their eggs 

 and seeds ; but experience has not confirmed this hypothesis; 

 and Professor Ehrenberg, our most expert microscopical in- 

 quirer, has never discovered any thing of the sort, although he 

 has met these microscopical objects where nobody before him 

 ever suspected their existence. (See his Organisation^ Sgste^ 

 >matik und Geographisches Verhdltniss der Infusionsthierchen, 

 1 Theil Berlin 1830. P. 79.) 



Dr Bostock, in his System of Physiology, vol. iii. (1827), af- 

 ter having stated the theory of equivocal generation as " very 



