1854.] 207 



When the intestines of a raccoon were filled with a solution of the acetate of 

 lead, and immersed in a solution of the bichromate of potassa, the deposit upon 

 the exterior consisted of innumerable small irregular granules, while that upon 

 the interior consisted of beautiful stellate crystals. 



When a sheep's bladder was rilled with a solution of the oxalate of ammonia, 

 and immersed in a solution of the chloride of calcium, no deposit took place in 

 the exterior iluid, whilst a precipitate of the oxalate of lime fell in the interior 

 flufd. 



The appearance of this under a magnifying power of 210 diameters, is repre- 

 sented in figure VIII. Within the muscular and fibrous coats of the bladder 

 this deposit presented the same appearance. The fact that solutions of certain 

 chemical substances will pass through a membrane in one direction, but not in 

 another, might be illustrated by many examples. 



The stomach of a raccoon was filled with a solution of the bichromate of potassa, 

 and immersed in a solution of the acetate of lead ; a copious deposit of the chro- 

 mate of lead took place in the exterior fluid, whilst none whatever occurred in 

 the interior; it retained its natural color and appearance. The results were in 

 all respects the same when the intestines of this animal were treated in a similar 

 manner. 



When the stomach was treated in this manner a deposit took place only upon 

 the interior. When the oesophagus of a large rattlesnake (Crotalus adamanteus), 

 was treated in a similar way, only a small deposit occurred in the exterior fluid. 

 Filled the stomach of a raccoon, and a portion of the intestines of a large 

 rattlesnake with a solution of the iodide of potassium, and immersed them in a 

 solution of the bichloride of mercury ; in both cases a copious deposit occurred 

 upon the exterior, whilst little or no precipitate fell in the interior fluid. 



These facts are due to one of two causes. Either certain chemical substances 

 in solution exert an influence upon mucous membranes, changing their minute 

 anatomical structure, and thus destroying their power of carrying on the physical 

 phenomena of endosmose andexosmose; or else mucous membranes possess a 

 power of choice, as it were, dependent upon their physical constitution, allowing 

 one fluid to pass through in one direction, but not another fluid holding a different 

 chemical substance in solution in an opposite direction. When a portion of the 

 small intestine of a sheep was filled with a solution of the nitrate of lime and 

 immersed in a solution of the oxalate of ammonia, a copious precipitate of the 

 oxalate of lime took place in the exterior fluid, which under a magnifying power 

 of 210 diameters was found to consist of innumerable octohedral crystals of dif- 

 ferent sizes, also a few dumb-bell crystals. The appearance of this deposit is 

 represented in figure VIII. 



In the exterior deposit the octohedra were about one hundred times more nu- 

 merous than the dumb-bell crystals. 



In the interior fluid a deposit of the oxalate of lime had taken place, which 

 under the microscope presented the appearance represented in figure IX. The 

 entire deposit consisted of innumerable minute and delicately formed dumb-bell 

 crystals, with here and there an octohedral crystal. In the interior fluid, unlike 

 the exterior, there were over a hundred dumb-bell crystals to one octohedral 

 crystal. Minute octohedra, and delicately formed dumb-bells, were found within 

 the meshes of the fibrous tissue. By comparing this experiment with the former 

 ones in which solutions of the same chemical substances were used, we are 

 forcibly taught the following laws. 



l?t. Mucous membranes from the same relative part of the bodies of different 

 animals, exert different physical influences upon the same chemical substances. 



2d. Mucous membranes from the same animal, but from different parts of 

 the body, exert different physical effects upon solutions of the same chemical 

 substances'. 



3d. The physical influence exerted by the membrane is not the same in 

 endosmose and exosmose ; it differs with the direction of the current. 



A very important question now presents itself for our consideration. May 

 not this change of form in the precipates be due to the presence of some animal 

 substance or fluid, as fibrin, blood, albumen, or serum, and no to the physical 



