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WHAT IS A TONIC ? 
BY EDWAED DIVEKS, M.D., E.C.S., 
PROFESSOR OF MATERIA MEDICA AND THERAPEUTICS IN QUEEN’s 
COLLEGE, BIRMINGHAM. 
T he most obvious reply to tbe question^ What is a 
tonic ? is^ — It is something which gives tone to the 
body. Unless, however, we know what is meant by tone,"’"' 
we are none the wiser for such a reply. What, then, is 
tone in a living being ? In its full signification, it is that 
elastic firmness which belongs to the soft parts of the body of 
a person in vigorous health ; — well seen, for instance, in the 
plump cheek of a robust child. f In a special sense, tone has 
been used to signify the state of a healthy muscle, when not 
producing motion, this being a state of strong tension— that 
is, that of an elastic body under a strain, through some resist- 
ance offered to its assuming a condition of equilibrium among 
its particles. Why tone is thus often limited in its use to 
the condition of the muscular parts of the body is soon 
explained. The muscles of a healthy living being are always 
on the stretch,"’^ or ready to contract when it is allowed to 
them, either by the approach of the points of their attach- 
ments, or by their severance from these, intentionally or 
accidentally effected ; and this, too, always in a much more 
marked manner than do any other structures of the body. 
Indeed, further than this, it is not to be doubted that much of 
the tension of some of these other structures is exhibited only 
because of their connection with, or contiguity to muscular 
organs. In considering, however, the nature of tonics, tone 
must generally be understood in its wider physiological sense. 
A state of tone is usually indicative of health and vigour of 
body, just as that of relaxation and flabbiness is indicative of 
disease, degeneracy, or loss of vigour. We have just remarked 
* rovog, strain, tension. 
t If a gash be made in the hving body, the edges of the wound will 
retract, causing it to gape, thus demonstrating in a simple manner that the 
flesh of the living body is in a state of tension. In the dead body this state 
has to a great extent disappeared ; consequently, when gashed, the incision 
does not gape. 
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