446 Dr. Griffith on the Sacculi of the Polygastrica. 



lected that the different portions of the intestinal tube or sacculi 

 are not stained, they are coloured from their cavitary contents, 

 their walls are colourless. M. Meyen's opinion concerning the 

 cilia I have not been able to verify ; but the rolling up of the 

 alimentary matters, whereby these masses rotate on their axes, 

 is never to be seen. The account given by Mr. Addison con- 

 cerning the action of liq. potassse is, as has been observed, very 

 remarkable. The best mode for the observer to perceive the 

 true effects of potassa on the Polygastrica is to use it slightly 

 diluted, for when used of the strength of the ordinary liquor 

 potassse, the effect takes place so suddenly as to lead to the in- 

 accurate interpretation of the appearances that gentleman has 

 given. The effect of the addition of this reagent, is solution of 

 the external covering of the animalcule, whereby the internal 

 elastic parts of the body, being liberated from the compression of 

 the external tunic, at first rush out, but are soon dissolved in the 

 same manner, when the alimentary matters remain. This phe- 

 nomenon is the result of the chemical action of the potash on the 

 substance of the highly elastic animalcule, most certainly not 

 of any imbibition or endosmosis. What are the conditions of 

 the fluids requisite for the production of this physical pheno- 

 menon? Difference in their density; the liquid in the cavity 

 towards which the fluid flows must be the most dense. The 

 cavity of the body, supposing such to exist, must contain a fluid 

 of greater density than that in which it floats or is suspended ; 

 in most of these Infusoria it is so at all times, and their medium * 

 being of extremely low specific gravity, almost equal to that of 

 distilled water, the most favourable conditions for the action of 

 imbibition are combined ; yet no endosmosis and consequent 

 bursting takes place. But we are told that when solution of 

 potash, a liquid of much greater density than that of the medium 

 in which these minute atoms are immersed, is added to their 

 ocean, imbibition does take place, their bodies burst; whereas we 

 have added the conditions requisite for the opposite effect, viz. 

 that of exosmose, and that this does not occur, the " bursting" 

 of the body of the animalcules proves. I believe the greater part 

 of the confusion which has existed on this subject has arisen 

 from considering the alimentary matters in different portions of 

 the intestinal canal as the dilated portions of that canal them- 

 selves. That these particles (stomachs) are cells which float in 

 the fluid of the body and elaborate the materials for its nutri- 

 tion, in the same manner as do those of the chyle and blood of 

 higher animals, may certainly be correct, but we have not the 

 slightest evidence of any analogy between them. The globules 

 of the blood and lymph are contained in those fluids, from whose 

 * I allude to the water in which they ordinarily exist. 



