THE BIOLOGY OF THE CELL SURFACE 



not onlv that he deals with dead matter but also that he 

 subjects the corpse to some thirty separate treatments 

 before he places sections of it under his microscope for 

 investigation. 



Hardy's paper nowadays hailed by so many as having 

 infallible authority falls short in three directions^: First, 

 Hardy studied the action of too few fixing solutions; second, 

 he failed to make comparisons of the fixed with the living 

 cells; and third, he used cells in bad condition. 



Every student of histology knows that he can not assume 

 that because he has successfully fixed cells of one tissue he 

 can employ this same fixation for every other kind of cell. 

 The technique of fixation has not passed very far beyond 

 the trial and error stage and, therefore, every new type of 

 cell encountered offers a new problem of fixation. Hardy 

 should have used more agents and of a much more diversi- 

 fied constitution Instead of holding so strictly to those of 

 closely related composition. 



Hardy made comparisons between the fixed cell (for 

 example, gut cells of Oniscus, the so-called pill-bug)^ and 

 protein solutions and came to the conclusion that his fixing 

 agents act upon the protoplasm as they do upon protein. 

 This conclusion revealed nothing new. It would have been 

 far more valuable had he made comparisons between the 

 living and the fixed cells In order to ascertain how far was 

 the deviation of the fixed from the normal. Further, Hardy 

 investigated always cells of tissues and never free-living 

 cells as Protozoa or eggs in their normal environment. This 



^ In his more thoroughgoing work Fischer contributed to our 

 knowledge of microscopic technique with respect to the use of dyes. 



- / may point to the fact that the choice of this object, gut cells of 

 Oniscus, was most unfortunate, for several reasons. These cells, for 

 instance, co7itain much chitin whose presence prevents uniformity 

 of fixation. See further: Scheikewilsch, i8g§; McMurrich, i8g§; 

 Conklin, iSgy. 



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