[Vor. 4 
220 ANNALS OF THE MISSOURI BOTANICAL GARDEN 
developed and complex organism. The ability to produce 
these compounds according to the needs of the organism has 
been demonstrated by the work of Abderhalden and his col- 
laborators, by Knudson, and others. We cannot compare the 
functions of a complex organism, such as the ability to pro- 
duce certain compounds in accordance with its need for them, 
or the ability to determine the course of extremely complex, 
yet complete, chemical reactions, with a function which the 
organism can perform only as an entity, such as self-reproduc- 
tion. We furthermore must not confuse ‘‘self-reproduction’’ 
in comparatively simple organisms, like the bacteria, with the 
produetion and reproduction of enzymes in the higher plants 
and animals. It is likewise true that many infectious dis- 
eases are associated with parasitism, but there are many 
which have not found an explanation in this cause. Examples 
of this in animals are measles, chicken-pox, mumps, scarlet 
fever, etc., while the group of ‘‘physiological diseases’’ of 
plants serves as an example for the vegetable kingdom. 
The fact that self-reproduction in a simple organism and 
the production of certain substances in a complex organism 
are two entirely different things is furthermore demonstrated 
by the following example. We are all familiar with the fact 
that the pathological condition characterizing diphtheria is 
attributable to the toxin produced by Bacillus diphtheriae 
which has lodged itself in the pharyngeal passages. If a por- 
tion of the toxin is injected into a normal individual, he will 
succumb to the pathological condition, 1.е., lesions of the 
heart, nerves, kidneys, etc., characteristic of diphtheria, and 
additional toxin will be produced in his system; yet no 
organism has entered into the case. The inflamed condi- 
tion of the throat will, of course, be absent, but this is 
largely the result of local irritation. Similar reactions occur 
in the production of serums, anti-bodies, and the like in other 
diseases, and it is upon the ability of an organism to produce 
and reproduce such complex substances and enzymes that the 
science of immunology is based. 
It is unfortunate that we have to go to the field of animal 
pathology for examples of this sort, but we are forced to do 
