206 [December, 



Figure IV. the acicular and octohedral crystals found in great numbers in 

 the aqueous humor of the eye. 



We see then by these microscopical examinations, that the oxalate of lime 

 has assumed forms different in all respects from those of the precipitate thrown 

 down, when solutions of the chloride of calcium and oxalate of ammonia are 

 brought into immediate contact. The precipitate thus formed consists of mi- 

 nute irregular granules. Figure V. represents this deposit. What has changed 

 the physical form of this deposit ? It has been accomplished, without doubt, 

 by the action of the membranes upon the chemical substances in solution pass- 

 ing through them. 



Experiments upon the physical influence exerted by mucous membranes, removed 

 from all vitality , upon chemical substances in solution passing through litem. 



Filled the intestine of a Raccoon, (Procyon lotor), with a solution of the 

 chloride of calcium, whose specific gravity was 1031, and immersed it in a so 

 lution of the oxalate of ammonia, having a specific gravity of 1007. In the 

 course of an hour the exterior fluids became cloudy, with a white precipitate, 

 the oxalate of lime. At the end of two days, a copious white deposit had settled 

 to the bottom of the jar, which, under a magnifiying power of 210 diameters, 

 presented the appearance of innumerable acicular, rectangular, and irregular 

 particles, often conglomerated together in great numbers, forming miniature 

 representations of plants with their branches and leaves. Figure VI. represents 

 their appearance. 



Specific gravity of exterior fluid 1005. 



The interior fluid was next examined, the intestine having been punctured 

 and its contents carefully removed. 



Specific gravity of interior fluid 1003. 



This marked change of its specific gravity from 1031 to 1003, shows that a 

 free interchange of the fluids must have taken place. The slight change in the 

 exterior fluid, of 1007 to 1005, is readily explained, when we consider the fact, 

 that the exterior was 12, whilst the interior was only 4 fluidounces. 



Within the intestines but a small deposit had taken place, in comparison with 

 that of the exterior fluid. Under the microscope this presented a magnificent 

 crystalline appearance, differing wholly from that of the exterior fluids, and also 

 from that formed when solutions of the chlorides of calcium and oxalate of am- 

 monia are brought into immediate contact. 



The appearance of this magnificent microscopical object is represented in 

 figure VII. 



Amongst the crystals there were no less than seven well defined regularly formed 

 varieties. We recognize the octohedral and dumb-bell crystals, as the form in 

 which the oxalate of lime almost invariably occurs in the urine, not only of man, 

 but also of other animals, and even in that of birds. 



Does not this experiment indicate that the peculiar forms of the oxalate of 

 lime, occurring in urine, may be the result of the physical action of the base- 

 ment membrane of the tubuli uriniferi and its secretory cells ? 



The tissues of the intestine were next examined. 



The cellular tissue was not equally injected ; in some places there was scarce- 

 ly any, while in others there was a very abundant deposit. 



In all places the mucous membrane appeared free from any deposit of the oxa- 

 late of lime. It was found difficult, however, to decide this question by the mi- 

 croscope, on account of the difficulty of separating the fibrous tissue completely 

 in which occurred a copious crystalline deposit. 



This is not the only instance ; out of numerous examples, we will select only 

 two. 



When the bladder of a raccoon (Procyon lotor) was filled with a solution of 

 the bichloride of mercury, and immersed in a solution of the iodide of potassium, 

 a brilliant red crystalline deposit of the biniodide of mercury took place upon 

 the exterior, whilst upon the interior a light yellow mass of lozenge-shaped 

 crystals of the protiodide of mercury was precipitated. In this case also the 

 mucous membrane appeared free from any deposit. 



