Measurement of Electrical Conductivity. 239 
Yet a further complication becomes obvious when we consider 
the so-called bio-electric phenomena in plants. These bio-electric 
phenomena have been much studied since Galvani’s famous 
experiments but in spite of a very voluminous literature dealing 
with these questions, little is really known about them. Recent 
work, more especially that of Nernst (26) and Beutner (3-8) and 
Loeb and Beutner (20-24), appears to throw more light on the 
subject. From the work of these authors it seems reasonable to 
regard living tissue as analogous to a complex of galvanic cells, 
and which should therefore behave in a similar way to the latter 
when a current is passed through them. 
The recent work of Hober (17, 18) has however indicated 
methods by which these phenomena may be eliminated, and 
enable us to obtain information regarding the interior of the cells. 
c, c. 
Fig. 5. In the primary circuit P, A is the spark gap of an induction coil ; 
C,, condensers; K, the coupling coil which couples the primary circuit to the 
secondary circuit S containing the capacity C 2 and self-induction L, in which 
is placed as core the vessel containing the electrolyte. T, the tertiary circuit 
containing the measuring instrument G. 
Hober’s work is based on the assumption that living cells 
possess a considerable internal conductivity, i.e., that a considerable 
part of the salts contained in them must be present as free salts. 
As however the passage of a current through a system of cells will 
be accompanied by polarisation at the surface of junction of two 
phases, the ordinary methods do not give any information regarding 
the conditions in the interior of the cell. The method used by 
Hober involves the use of waves instead of a low-frequency 
alternating current. Various modifications have been used, the 
development of the methods being quite a unique example of 
adaption of physical science to physiological purposes. The 
principle involved in one of Hober’s earlier methods consisted in 
the production of waves in a circuit containing self-induction and 
capacity. The damping of the waves which was produced by using 
a suspension of cells as core in the self-induction was measured. 
