ALIMENTARY SYSTEM. 



37 



Fig. 16. 



u 



pass over a subject of so much importance without expressing ourselves 

 as being far from admitting their accuracy, and we must say that our 

 own observations upon the structure of the polygastria have led us to 

 very different conclusions*. 



(75.) The positions of the mouth 

 and anal aperture we are well 

 assured, by frequent examination, 

 to be such as are indicated by the 

 illustrious Professor of Berlin ; but 

 with regard to the tube named by 

 him intestine f, and the stomachs 

 appended thereto, our most patient 

 and long-continued efforts have 

 failed to detect the arrangement 

 depicted in his drawings. In the 

 first place, as regards the function 

 of the sacculi, which he looks upon 

 as the organs in which digestion is 

 accomplished : in carnivorous ani- 

 malcules, which devour other spe- 

 cies, we might expect, were these 

 the stomachs, that the prey would 

 at once be conveyed into one or 

 other of these cavities ; yet, setting 

 aside the difficulty which must 

 manifestly occur in lodging large animalcules in these microscopic sacs, 

 and having recourse to the result of actual experience, we have never 

 in a single instance seen an animalcule, when swallowed, placed in 

 such a position, but have repeatedly traced the prey into what seemed 

 a cavity excavated in the general parenchyma of the body. 



(76.) In the second place, the sacculi have no appearance of being 



* Perhaps some of our readers may think the above strictures upon the opinions 

 of Professor Ehrenberg, which appeared in the first edition of this work, and have 

 been written upwards of twenty years, have now become rather antiquated. It is, 

 however, the wish of the author to combine some account of the progressive advance- 

 ment of our knowledge relative to interesting or disputed points of microscopical 

 research with an exposition of the views generally adopted by physiologists of the 

 present day ; and as the above were the first arguments advanced against the then 

 universally received opinions of the distinguished author of the ' Infusionsthierchen,' 

 it has been deemed expedient to retain them in their original words. It may be 

 proper to state that the microscope used in these and similar researches to which 

 allusion will be made, is a compound achromatic, made by Boss, of London; and 

 the powers employed, of -^, , \, and i of an inch focus. 



f Since the above was written, Professor Ehrenberg has been kind enough per- 

 sonally to exhibit to the author his preparations of the central tube in several species 

 of animalcules. The author's views, however, relative to the nature of the so-called 

 stomachs remain unchanged. 



