THE PROTOPLASMIC SYSTEM 



fact warrants my third objection to his conclusions for two 

 reasons: First, his cells were already in some state of post 

 mortem changes of greater or lesser degree depending upon 

 the time elapsing between their removal from the animal 

 and their fixation — these changes being more rapid, and, 

 therefore, a more serious source of error, for tissue-cells 

 removed from the warm-blooded animals which he used. 

 In the case of warm-blooded animals it would also make a 

 great difference whether or not the animal from which the 

 tissues were removed, was anaesthetized. Second, he made 

 no allowance for the bulk of tissue used; that is, his con- 

 clusions would have been far more sound had he used a thin 

 sheet of tissue made up of a layer of one or two cells instead 

 of compact masses from the glands investigated. Not only 

 were his cells In some degree of post mortem change, but also 

 were they fixed unevenly and cut into sections of different 

 thickness. 



True, there is bad and unreliable fixation of eggs. Never- 

 theless, it is erroneous to condemn all fixation. If I find 

 that after fixation an egg very closely resembles the living 

 I can draw conclusions on the basis of this resemblance espe- 

 cially since knowing that the cell is dead I take into con- 

 sideration that its proteins are changed — coagulated, 

 gelated, precipitated, and that still other changes have 

 taken place. Instead of abandoning the study of fixed 

 cells we should use proper fixation in order to check and 

 extend observation on the living. Neither the cinemato- 

 graph nor tissue culture will quite replace the good fixation 

 of the cell for comparison with the living. 



Although our ignorance of the ground-substance is pro- 

 found and will remain so until we study it frankly as such,^ 

 isolated from all the coarse particles suspended in it, never- 

 theless we have at our disposal certain evidence which may 



1 Jvst, 1 93 6b. 



67 



