on the Porosity of Bodies. 291 



morphologically requires further clearing up, inasmuch as the 

 apertures in the substance of the textures necessarily assumed, 

 from the occurrences above mentioned, could not until now be 

 demonstrated. 



After many fruitless attempts, I have been so fortunate as to 

 discover in the substance of all organic bodies already formed, 

 microscopic spaces from yoVo'" ^^ i;oVo'" (Paris line) in dia- 

 meter, and generally in all the bodies which I have examined, 

 to recognize signs of an optically demonstrable and measurable 

 microscopic porosity. Referring, then, to my more ample re- 

 presentation given in the above-mentioned paper, and to the 

 delineations which accompany it, I beg leave here to offer a 

 short description of the simple methods followed by me in my 

 researches, and of the results. 



While reflecting on the difficulties which, notwithstanding the 

 perfection of modern microscopes, opposed themselves to the 

 attainment of the long-striven-for end in question, I feared most 

 of all that, with our present means, the objects to be examined 

 could not be finely enough divided to make the spaces between 

 their particles plain. Manifold as had been the searches after 

 pores, there was nothing to make it probable that their perfora- 

 tions were in a perpendicular direction. It seemed much more 

 likely that they ran in directions the most varied, of the sloping 

 and oblique, perhaps even zigzag, for it had been suggested by 

 Henle*, that the pores of the epidermis " might perforate the 

 skin obliquely," and on this account be imperceptible. Further, 

 it was clear that even a thin animal membrane, but which con- 

 sisted of several layers of different fibres, forming a texture far 

 more perfect than the artificial ones wrought by the hand and 

 machines of man, must indeed have spaces between its fibres ; 

 but that so long as the different layers of that texture ran over 

 and through one another, it would be difficult with certainty to 

 discern those spaces. So that, although having at command 

 even the best illumination, and with a microscope of the first 

 order, he who might attempt to search out the pores of an 

 animal membrane, would find himself going astray just as much 

 as one who endeavours to see through a board ; for both con- 

 sist of variously twisted fibres covering one another, the spaces 

 between which nothing but very minute division can bring 

 into view. 



But further, as all bodies by no means possess a fibrous 

 structure, and as even organic fibres, so far as they undergo 

 change of material and through moisture swell and are filled 

 out, must likewise themselves be porous, it was evident that 

 through perception of the spaces between the fibres the porosity 

 * Allgemeine Anatomic, 1841, p. 237. 

 U2 



