36 DR. A. D. WALLER ON THE 
$3. Of the additional pieces of apparatus just referred to, the 
first (marked R) is for the purpose of letting a blaze-eurrent 
into the galvanometer-circuit at a short and regular interval 
after excitation by a break induction-shock. 
The other (marked B A C) is for the purpose of taking 
the separate post-anodie or post-kathodie effects at A or at B, 
after excitation ihrough A and B. By a movement of the 
switch, contact at one or other of these excited points is 
replaced by a contact C with an indifferent point. 
$4. The purpose of a standardising deflection is two-fold :— 
A deflection taken before and after experiment serves to show 
whether the resistance has altered, and how much. 
The currents observed in different experiments are, to some 
extent, brought to a common denominator when they have been 
referred to and expressed in terms of a standard voltage. 
I say “to some extent," for it is evident that a reduc- 
tion to zero by a compensating current, or a comparison of a 
blaze deflection with a standardising deflection, can never give 
us the true electromotive value of our physiological currents. 
We do not know how much of our mass is actually active, 
nor in what proportion the mass offers a shunt to the galvano- 
meter. 
Nevertheless, with this distinct understanding, that a de- 
nomination by voltage does not signify that we have measured a 
physiological voltage, it is evidently better to specify effects in 
terms of voltage than in terms of eurrent. 
$5. Seconp Day.—The first object I have in view is to 
compare land-plants with sea-plants as to their blaze-currents ; 
so I visit the garden to select some convenient land-vegetable 
from whieh to obtain a constant supply of fresh material: c'est 
lembarras du choix; finally I select peas as my principal 
vegetable, although I foresee that it will be quite impossible 
to remain attached to peas alone. 
$ 6. I visit the sea-shore at low tide, to select some convenient 
sea-vegetable from which to obtain a constant supply of fresh 
material: the choice is not so various. Finally I select a sea- 
weed, the name of which I do not know, but which exists 
in luxuriant abundance attached to the rocks at half-tide, and 
is charaeterised by quantities of olive-shaped ovaries, somewhat 
like pea-pods. They will therefore afford a quite satisfactory 
