172 ON THE INTERNAL FORM AND [ch. 



But here we touch the brink of a subject so important that we must not 

 pass it by without a word, and yet so contentious that we must not enter into 

 its details. The question involved is simply whether the great mass of 

 recorded observations and accepted beliefs with regard to the visible structure 

 of protoplasm and of the cell constitute a fair picture of the actual living cell, 

 or be based on appearances which are incident to death itself and to the 

 artificial treatment which the microscopist is accustomed to apply. The great 

 bulk of histological work is done by methods which involve the sudden killing 

 of the cell or organism by strong reagents, the assumption being that death 

 is so rapid that the visible phenomena exhibited diu'ing life are retained or 

 "'fixed"' in our preparations. While this assumption is reasonable and 

 justified as regards the general outward form of small organisms or of individual 

 cells, enough has been done of late years to shew that the case is totally 

 different in the case of the minute internal networks, granules, etc., which 

 represent the alleged structure of protoplasm. For, as Hardy puts it, "It is 

 notorious that the various fixing reagents are coagulants of organic colloids, 

 and that they produce precipitates which have a certain figure or structure,... 

 and that the figure varies, other things being equal, according to the reagent 

 used." So it comes to pass that some writers* have altogether denied the 

 existence in the living cell-protoplasm of a network or alveolar "foam"; 

 others t have cast doubts on the main tenets of recent histology regarding 

 nuclear structure ; and Hardy, discussing the structure of certain gland-cells, 

 declares that "there is no evidence that the structure discoverable in the cell- 

 substance of these cells after fixation has any counterpart in the cell when 

 living." "A large part of it " he goes on to say "is an artefact. The 

 profound difference in the minute structure of a secretory cell of a mucous 

 gland according to the reagent which is used to fix it would, it seems 

 to me, almost suffice to establish this statement in the absence of other 

 evidence." 



Nevertheless, histological study proceeds, especially on the part of the 

 morphologists, with but little change in theory or in method, in spite of these 

 and many other warnings. That certain visible sti'uctures, nucleus, vacuoles, 

 "attraction-spheres" or centrosomes, etc., are actually present in the living 

 cell, we know for certain; and to this class belong the great majority of 

 structures (including the nuclear "spindle" itself) with which we are at present 

 concerned. That many other alleged structures are artificial has also been 

 placed beyond a doubt ; but where to draw the dividing line we often do not 

 know j. 



* F. Schwartz, in Cohn's Beifr. z. Biologie der Pflanzen, v, p. 1, 1887. 



t Fischer, Anat. Anzeiger, ix, p. 678, 1894, x, p. 769, 1895. 



J See, in particular, W. B. Hardy, On the structure of Cell Protoplasm, Journ. 

 of Physiol. XXIV, pp. 158-207, 1889; also Hober, Physikalische Chemie der Zelle 

 uiid der Gewebe. 1902. Cf. (int. al.) Flemming, Zellsubstanz, Kern und Zelltheilung 

 1882, p. 51, etc. 



