MEMOIR XXVI.] CAPILLARY ATTRACTION, ETC. 



355 



Fig. 79. 



no hydrostatic pressure either one way or 

 the other through the pores of the perito- 

 neum, as soon as the arrangement is com- 

 pleted, if the observer be so placed as to 

 view it by transmitted light, he will see 

 the water descending through the pores of 

 the peritoneum in striae and streams in a 

 perfectly colorless state. The membrane 

 has, therefore, absorbed and transmitted 

 the water, but has refused to the coloring 

 matter a passage. Such illustrations may, 

 therefore, satisfy us that the selecting pow- 

 er of organic textures, like that of inorganic fj 

 ones, is dependent on simple physical cir- 

 cumstances, and for these reasons we may 

 exclude from the mechanism of animal ab- 

 sorption the influence of any vital or other mysterious 

 principles, and adopt the opinion of Abbe Hauy, that 

 "those specious causes and imaginary powers to which 

 in the Middle Ages all natural phenomena, even those of 

 an astronomical kind, were referred, but which, through 



/ ft O 



the genius of Newton and Laplace, have been banished 

 from the celestial spaces, have taken their last refuge in 

 the recesses of organic beings, and from these retreats 

 science is preparing to expel them." 



We may next turn to an examination of analogous phe- 

 nomena in the case of gases. I found that on blowing a 

 little bubble of melted shellac on the end of a glass tube, 

 and putting some reddened litmus- water in its interior, 

 ammoniacal gas, to which it was exposed, could almost 

 instantly permeate the thin texture or barrier, and, gain- 

 ing access to the inside of the bubble, turn the litmus 

 blue. 



When the pores of such barriers are of sensible size, 



