on the Porosity of Bodies. 876 



with this subject that lasted many months, I met with no scrap- 

 ings in which unequivocal pores were entirely missed. 



But with respect to the objections which many will feel in- 

 clined to aim at the correctness of my statements, they have 

 been mentioned briefly in the foregoing, and amply treated of 

 and met in my paper ; so that to avoid being too diffuse, I must 

 refer thereto. As for the rest, I am convinced that practised 

 observers, should they determine with their own eyes intimately 

 to test the accuracy of my statements according to the above 

 described methods, will be directly led to the firm conviction 

 that the porous structure of the particles is not the product of 

 mechanical division into minute parts, but a natural formation, and 

 that the porosity perceptible in the same is no optical illusion. 



Among the organic and inorganic bodies examined by me 

 according to the above methods, I would especially mention the 

 shell and membranes of the egg, the epidermis and cutis of man 

 and many animals of different classes ; further, horn formations, 

 hair, the cell-membrane, the mucous and vascular membranes, 

 the walls of capillaries, lymphatics, blood-corpuscles, serous 

 membranes, ligaments, bones, and teeth. Further, my examina- 

 tions have extended to all parts of plants, in the course of which 

 I repeatedly discerned the microscopic pores most definitely in 

 the roots. In my paper already mentioned, plate 1. figs. 6, 7, 8, 

 represent the microscopic pores of the outer layer of a white 

 bean, of a potato-peeling, and of cork. Lastly, of the vegetable 

 formations examined, I have to mention charcoal, pit coal, and 

 brown coal. Of the inorganic bodies whose microscopic pores I 

 have found, I would make especial mention of gold, tin, silver, 

 lead, iron, granite, many crystals, &c. My paper, in plate 1. 

 figs. 10, 11, contains drawings of the microscopic pores of gold 

 and of iron. The pores of granite measure yaV o'" (^' ^* Pa^'is 

 line) in diameter, those of iron 20V0'" ^^ ToVo'" > those of steel, 

 which however are very difiicult of demonstration, appear to be 

 still somewhat smaller. The average size of the pores in all 

 vegetable formations may be taken at yjW'", among which 

 there occur individual variations of from toVu *^ 2 o^(jo'"' "^^^ 

 pores in animal formations as to size do not widely differ from 

 those of plants ; they appear however to be a trifle larger. In 

 the shell of the hen^s egg they measured g Jo"' *^ 2 oVo"^ i^ *^^ 

 membrana test^ on the average jsqq'", in the membranes of the 

 ovum of Man and the Rabbit ygVo'" ^^ tug's'" > ^^ ^^^ human 

 cuticle and skin the same. The pores of the epithelium and 

 mucous membranes had the same size, while in the epithelium 

 and all other layers of the vessels I remarked and measured 

 pores from y^^o ^^ 2 oVo'''^ ^^ individual cases however even 

 large rifts or clefts from -^^fj'" to s^jj"'* The pores of the lym- 



