368 Transactions of the Society. 



that behaviour with the existence of a formed cell-membrane, and 

 indeed no better proof could be required of the entire ground- 

 lessness of the belief in a cell-membrane than that afforded by fat- 

 absorption. This belief in a cell-membrane has arisen and been 

 maintained by false analogy and erroneous histological methods, 

 or through the interpretation of the appearances they produced. 

 Asa vegetable cell often possessed a cell-wall, so it was supposed 

 that an animal cell ought to possess one, although the com- 

 plete organisms of plant and animal are entirely unlike. His- 

 tologically it was, or rather it is at the present time, considered 

 sufficient to treat fat-cells with ether, which dissolves out the fat 

 from the fat-cells and leaves the empty envelopes behind, and these 

 are held to be complete evidences of the existence of a cell- wall. It 

 is somewhat surprising to find histologists at the present day, who 

 make a sine qua nan of the use of fixing agents, admitting such a 

 proof. Ether, like alcohol, is a fixing agent which first fixes the 

 protoplasmic envelope and destroys its power of contraction, then 

 dissolves out the fat within it. 



Certainly the histologist in this case has made a membrane 

 where one did not naturally exist, but the explanation is so simple 

 that it is surprising that no one ever noticed the worthlessness of 

 the test. Kanvier, while saying that this test is perfectly demon- 

 strative, adds another of his own invention, which is equally mis- 

 leading. By his well-known method of interstitial injection of a 

 solution of nitrate of silver among the fat-cells lying in the sub- 

 cutaneous tissue, he holds that he has been able to demonstrate the 

 existence of a cell-membrane external even to the protoplasm 

 distended round the fat. Under this treatment a dark membranous 

 layer seems indeed to surround the cell, but here too the appear- 

 ances are deceptive and the interpretation incorrect. When a 

 solution of silver is allowed to come into direct contact with such 

 cells, it forms such a layer where none existed before. This may 

 easily be demonstrated upon an endothelium-covered membrane, as 

 we have often done. If at one part the endothelium be removed 

 where it covers fat-cells, and the silver solution be then applied, it 

 will be found that the unprotected fat-cells show the dark pseudo- 

 membrane where the silver solution had come in contact with them, 

 while the contiguous fat-cells which were protected by endothelium 

 show no such membrane, thereby proving that the supposed mem- 

 brane is only an artificial production. Where the silver has thus 

 only penetrated to a certain distance into the protoplasmic wall, the 

 unafiected portion retains its normal appearance, and thus gives 

 rise to the supposition that a part of the original protoplasm may 

 often be seen lying on the inner surface of the supposed membrane. 



The expression referred to, that the cell-wall only gets formed 

 when the fatty contents have pushed the protoplasm and nucleus 



