Professor J. W. McLaughlin, M. D. 
73 
wave energies are mutually equalized. But the condition of the 
molecules of the surface of the mass is quite different from those 
of the interior, since their waves are not equalized, but remain free 
and active. I call this free energy of surfaces, catalytic energy. Its 
intensity is in direct proportion to the surface of the mass and in 
indirect proportion to mass itself. Colloids, colloidal platinum, etc., 
enzymes, pathogens, toxins, and albumins, all belong to the colloidal 
class and possess catalytic energy. 
“Emil Fischer, in his experimental work with sugars, has clearly 
shown that the action of an enzyme is specific. Enzyme and sub- 
strate must bear a definite relation one to the other. Susceptibility 
of a substance to a ferment required not only a definite chemical 
structure, but a definite stereo-chemical configuration of molecules. 
Now, bearing in mind this specific relation, it may be seen that the 
non-immune organism must contain many substrates; and that these 
are either different tissues or one composed of many isomers. I have 
assumed that the albumins of the blood serum and tissue juices are 
made up of groups of homologous molecules that are isomers, that 
is, they are alike in chemical structure - , but differ one group 
from the other in the spatial arrangement of their contained atoms. 
It is made clear by the behavior of a ferment — maltose toward the 
A. and B. series of glucosides that this feature of molecular struc- 
ture changes the vulnerability of the substrate to organic catalyzer 
— say a pathogen. Each group of albumins in the blood serum will 
furnish a specific substrate which differs from others in vulnerabil- 
ity to microbic action. There is no absolute proof of the truth of 
this concept, but it is supported by the following evidence : There are 
important differences between immune and non-immune blood serum, 
the nature of which is not known — the blood serum of different 
species is not the same. This fact is used in medico-legal cases to 
determine the origin of blood — whether from a man or beast. The 
nature of these differences in sera is not known, but it is known 
that the serum of one species may be immunized against that of 
an alien species by small frequent inoculations. Just as it may 
be against a pathogen of toxin; the reaction brought about in the 
blood of the non-immune animal is definitely specific. 
“The blood serum and other tissue juices furnish the pabulum 
from which all the tissues of the body receive nourishment for repair 
of waste and functional action, and it is * inconceivable how tissues 
of such a heterogeneous character can each receive particular nour- 
gishment from a homogenous pabulum, but when we regard metabolism 
as catalytic, the tissues being organic catalysts, and the blood serum 
