The Mieroseo^ie Germ Theory of Disease. By H. C. Bastian. 69 
to my recently published work, * Evolution and the Origin of 
Life.' 
Some time must be allowed to elapse before anything approach- 
ing to general agreement can be expected on such a subject ; and 
meanwhile, standing as we do in the face of opposite doctrines as to 
the nature of ferments, we are free to look into the question of the 
relation of the lower organisms to disease on its own merits, apart, 
that is, from the overweening influence of any general theory of 
fermentation. 
Leaving on one side, therefore, the influence of the analogy 
deemed to exist between the process of fermentation and that of 
zymosis, we may ask what other general evidence is forthcoming 
in favour of the notion that contagia are low organisms or living 
unitSj rather than dead organic particles from altered tissue-ele- 
ments, or complex chemical compounds of alkaloidal constitution 
engendered in the tissues or in some of the fluids of the body. The 
consideration of this question may be introduced by a quotation 
from Dr. Burdon-Sanderson's valuable Keport on the "Intimate 
Pathology of Contagion." * He says : " There are two obvious 
objections which stand in the way of the acceptance of any chemical 
explanation of the phenomena of contagion. The first is, that the 
multiplication of contagium in the body of the infected individual 
is a process which cannot be compared to any which is brought 
about by chemical agencies independently of organic development. 
The second is, that all contagia possess the power of retaining their 
latent virulence for long periods (often resisting the most unfavour- 
able chemical and physical conditions), and only show themselves 
to be what they are when they are brought into contact with [the] 
living organism. Outside of the body the contagious material 
withstands all those changes to which, on chemical grounds, we 
should expect it to be liable ; while in the body it manifests a 
degree of activity, and gives rise to an amount of molecular dis- 
turbance, which is quite as unaccountable Neither of these 
difficulties stands in our way if we suppose that the contagious 
process is connected with the unfolding of organic forms T 
Now, though this is about as strong a statement as can be 
made, from an a priori point of view, against the mere chemical 
action of contagium, and in favour of a germ theory, I must confess 
that neither of the considerations seems to me to carry very much 
weight with it. I should be inclined to say, in reply (1) that proof 
is altogether wanting of the " multiplication of contagium " in the 
body in the same sense that a living unit multiplies ; and that 
there are physico-chemical processes which may illustrate what 
occurs when contagium increases within the system. Instead of 
being an increase by continuous organic development and multipli- 
* ' Twelfth Report of the Medical Officer of the Privy Council, 1870,' p. 243. 
