PRINCIPLES OF GENERAL PHYSIOLOGY 



parts of protoplasmic organisms, are examined under the microscope, they are seen 

 to be in constant movement. This phenomenon was first noticed by the botanist, 

 Brown (1828, p. 359), and is therefore called "Brownian movement." Its nature 

 will be discussed in Chapter IV., but its existence shows that the particles in 

 question are suspended in liquid, and not held in a network or other kind of fixed 

 structure. On the death of protoplasm, as Gaidukov points out (1910, p. 62), the 

 movements cease, and a precipitation or coagulation, like the " setting " of gelatine 

 when it cools, occurs ; in the words of Graham, the hydrosol has become a 

 bydrogeL 



Further evidence in the same direction is afforded by the mode of respoiiM \ 

 protoplasm to an electric shock. When such a stimulus is sent through an amn-b.-i. 

 it is made to draw itself together so that its surface shall be the least possible, 

 in fact it becomes more or less spherical (Kiihne, 1864, p. 32). This would be 



impossible if struct uiv> 

 incapable of movement. 

 over one another were 

 ]>irsi-iit. Similar chan^i > 

 are seen in the stamina! 

 hairs of Tradescantia 

 (Fig. 5). 



Certain organisms known 

 as mycetozoa in one stage 

 of their life history, form 

 masses of naked protoplasm. 

 One of these, Badliamia, 

 found on logs of decayed 

 oak, was investigated \>v A. 

 Lister (1888). It is usually 

 full of the dark brown spores 

 of the fungus on whieh it 

 feeds, but it ran he made 

 to creep through wet cotton 

 wool, whirli filters out the 

 spores and clarities tin- pioto- 

 plasm. It is difficult l<> 

 understand how a sultstan'-c 

 other than a liquid could 

 be separated up into fine 

 threads, which immediately 

 run together again to form a 

 mass like the original one, 

 but devoid of the suspended 

 bodies. 



G. L. Kite (1913) states 

 that Congo red and other 

 dyes, injected into the interior of an anuvba, diffuse rapidly throughout the protoplasm. 



Although we are thus compelled to look upon protoplasm as a liquid, it shows 

 under intense, oblique illumination ("ultra-microscope") that it is not homo- 

 geneous like water, or solutions of sodium chloride. On the contrary, it contains 

 an immense number of minute particles, seen by this method (also called " dark 

 ground illumination ") as shining points, or diffraction discs (Fig. 6). There are 

 present, therefore, substances in what we shall learn to recognise as the colloidal 

 state. It is to be noted that the protoplasm in the upper of the two figures given 

 is quite clear and homogeneous when ordinary methods of illumination are used, 

 even under the highest magnifications. 



Similar conclusions are drawn by Mott (1912) from observations on living 

 nerve cells by the same method. 



It is unfortunate that the study of the phenomena presented by living cells is rendered 

 difficult by the fact that so little can be seen by microscopic observation. A few words may, 

 therefore, be useful here as to the nature of microscopic vision. 



FIG. 6. CELL OF SPIROGYRA. 



A, under ordinary illumination. 



/?. under brilliant dark ground illumination ("ultra-microscope"). 



The protoplasm appears clear and structureless in A ; full of minute 

 granules in B. Length of cell, O'OSC mm. 



(After Gaidukov.) 



