70 The Microscopie Germ Theory of Disease. By H. C. Bastian. 
cation, it may be that contagium augments by some such process 
as that by wbicb crystals of sulphate of soda increase or " multiply " 
when a fragment of such a body is thrown into a complex fluid 
containing its component elements. This is confessedly a very 
imperfect illustration, and one to which I resort merely to indicate 
the possible occurrence of another mode of increase of contagium 
within the body ; though in an infected animal such increase may 
occur in a much more subtle manner, owing to the fact that fluids 
altered, directly or indirectly, by the original contact of contagium 
with some part of the body, are either locally or generally brought 
into intimate relation wdth the active, though modifiable, living 
units of the various tissues. And (2) in reply to Dr. Sanderson's 
other objection, which stands, as he supposes, in the way of any 
chemical explanation of the phenomena of contagion, I should say 
that, although our knowledge is at present extremely vague con- 
cerning the power possessed by the various contagia of retaining 
their virulence for long periods, and of resisting unfavourable 
physical and chemical conditions, we have no reason to believe that 
the more complex combinations of which living matter is composed 
are capable of resisting influences which would prove destructive to 
less highly complex not-living substances, such as snake -poison, 
woorara, or other compounds of this class. The general evidence 
is therefore, as I read it, certainly not more favourable to a vital or 
germ theory than to a physico-chemical theory as regards the 
nature and action of contagia. 
I should here point out, however, that under the term " germ 
theory " two distinct views are included, each having their advocates 
amongst distinguished members of this Society. The side to which 
Dr. Sanderson leans is sufiiciently obvious. Speaking of contagious 
particles, he says : * " With reference to their mode of action, we 
have examined into those considerations which seem to render it 
probable that they are organized heings, and that their powers of 
producing disease are due to their organic development ; and we 
have accepted this doctrine as the only one which afibrds a satis- 
factory explanation of the facts of infection." j 
This is the doctrine with which we are at present especially 
concerned, though it may be well for me to say a few words con- 
cerning the other sense in which a " germ theory of disease " is 
maintained by a distinguished member of this Society. Dr. Beale 
says : + " We have therefore now to inquire what is the material 
substance which passes from the diseased to the healthy organism 
* Loc. cit., p. 255. 
t TPiGse words occur in a summary which, it is only right to add, was im- 
mediately prefaced by the following slatement: "The sentences which follow 
niu.st therefore be accepted by the reader as nothing more than indications of the 
questions we are trying to solve^ or as forecasts of what we hope to establish or 
(lisprove by experiment." 
X 'Disease (xerms, their Keal Nature,' 1870, p, 5. 
