'y^'^^^ on the Porosity of Bodies. ''^ -^ WT 



mechanical pressure may follow. Here too belong the penetra- 

 tion of entozoa and their ova into the blood, — the penetration 

 of molecules of mercury, fat-globules, even finely pulverized 

 solid bodies, through the pores of the epidermis and of the 

 mucous membranes, — the passing out of blood- globules through 

 the loosened capillary walls in menstruation, — the pressing 

 through of blood-corpuscles in bloody secretions, in pneumonia, 

 &c., — the penetration of the materials of disease into the blood 

 through the outer skin and the mucous membranes, — the finding 

 in the blood of substances introduced, &c. 



With regard to vegetable physiology, and in respect of the 

 experiments long since instituted by Stephen Hales and very 

 recently confirmed by Liebig*, I must give utterance to the de- 

 claration, that since my discovery of the visible and measurable 

 microscopic pores in all vegetable formations, the currents therein 

 may with ease be referred to the physical agencies of capil- 

 lary attraction, evaporation, &c., without requiring with Du- 

 trochetf to have recourse to an active mysterious vis a tergo 

 to explain the rising of the sap. In this manner of viewing the 

 vegetable organism, it appears to us an exquisitely constructed 

 machine indeed, yet set in motion chiefly by means of simple 

 physical forces, — a machine whose universally-diffused porosity 

 permits as well the ascent of the fluids out of the earth sur- 

 rounding the roots, as also the evaporation of the plasma satu- 

 rating all vegetable formations, according to physical laws. 



I have the additional remark to make, that my paper in ques- 

 tion, plate 1. fig. 5, contains a drawing I made, faithfully de- 

 lineating nature, the result of numerous observations, of the 

 Aspidogaster conchicola (Baer) living in the pericardium of Unio 

 and Anodonta, in which may be observed the pressing through 

 of the granular molecules out of the intestinal cavity into the 

 substance of the body ; a process that may be not only observed, 

 but followed through all its stages, during lifeJ^ 



Confirmations. 



In testing the accuracy of Keber^s observations, so far as my 

 health permitted, I used a J-th-inch object-glass, very lately 

 made for me by Smith and Beck. Of the performance of this 

 object-glass, I need say no more than that the order for it was 

 given by my esteemed friend J. J. Lister, — that it was submitted 

 for his approval before the fitting on, — and that he wrote to me 

 concerning it : — '^ I can report with much satisfaction of its 

 quality — its correction and defining power being all I should 



* I. c. p. 72, &c. 



't' U agent immediat du mouvement vital, 1 826, p. 90. 



Phil. Mag. S. 4. Vol. 8. No. 53. Nov. 1854. 3 C 



