J893.] NEW-YORK MICROSCOPICAL SOCIETY. 33 



ichanges is due only to the imperfection of our apparatus and 

 methods. Even the special absorption of certain stains by the 

 living protoplasm of plants and animals is almost always attended 

 with extreme irritation and then their death by poisoning ; it is 

 not yet safe to assume that such a death is not accompanied by 

 morbid change, however imperceptible hitherto, in many cases, 

 by our best skill in observation. 



Partial success, it is true, has been obtained by the use of 

 ■paralyzing reagents, such as cocain ; but in general, as Hofer 

 observes, " a simultaneous swelling of the protoplasm occurs, so 

 that, although the topographical conditions are retained, the his- 

 ■tological details are in many cases destroyed." 



A general acknowledgment of the fact, therefore, that a mount- 

 ed preparation, however useful as an accessory source or illustra- 

 tion of special facts, can only be a mummy, or a slice of a mum- 

 my, never a satisfactory substitute for the living protoplasm of the 

 original tissue or organism, would have a tendency to clear the 

 air of much controversial vapor, our literature of interminable 

 'discussion, and our life work of a vast amount of wasted labor. 

 It seems at first discouraging, but I think it is true. 



The partial success in the past, however, leads us to hope that, 

 ■by more systematically devised processes and formulse. We may 

 succeed in arresting protoplasmic change so speedily and thor- 

 oughly, as to cause the organisms embalmed in our cells to re- 

 tain a far more life-like approximation to their original structure. 

 To this end, precaution must be taken to guard against the causes 

 of distortion yet to be considered. 



2. Contraction by Chemical Reaction. — The jelly-like contents 

 of the cells may be diminished by slow solution or by chemical 

 reactions gradually produced through some constituent of the 

 surrounding medium. Alcohol, in any proportion, should there- 

 fore be omitted, on account of its known solvent action upon 

 chlorophyll and other coloring matters ; its dilution signifies only 

 delay in solvent attack. Any acid, moreover, especially if inor- 

 ganic (with a few exceptions, like carbon dioxide), has a ten- 

 dency to produce contraction ; this apparently consists of actual 

 disintegration and destruction of sarcode in time, particularly 

 rapid in that of protozoa, amoeba, and the coelenterata. This 

 ■tendency may be very u-seful in bringing out certain structures 



