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organism, is true in certain cases, at least for the higher animals. 
Non-hereditary immunity might be caused by freely moving enzymes, 
unable to enter the cells. 
Van CALCAR’s opinion that the anti-bodies of the serologists are 
ferments, that is enzymes, is thus undoubtedly right. He says: *) 
Whichever immunity reaction is examined, it is constantly found that 
the whole course of these reactions depends on the action of two 
substances, one of which having in all respects the character of a 
ferment, the other that of an enzyme-substrate to be decomposed 
by that ferment. The ferment-like substances are called ‘“‘anti-bodies”’, 
the various substrates they act upon, “antigens”. | 
In my opinion there is however no sufficient ground also to call 
the antigens and the complement “enzymes”, as is done by several 
investigators. 
If these substances are considered as enzymes only because of 
their action after injection into the blood of higher animals, it will 
be necessary, in order to be consistent, likewise to bring to the 
enzymes toxins and even some common coagulable proteids, which 
would make this word lose its real significance. Whereas in the 
descriptive sciences the necessity is felt to designate by special 
names even but slightly differing objects, it would be an error to 
attribute to the words enzyme and ferment a continually varying 
and wider meaning no more in accordance with the original con- 
ception. On the other hand it is clear that further knowledge about 
the enzymes or factors may necessitate the creation of néw names 
to mark the vast differences between them, as now we are already 
compelled to use the words exo- and endoenzymes. 
There is still another group of bodies worth being considered from 
the new point of view, namely the viri in general and in particular 
those of plant diseases, such as the mosaic disease of the tobacco. 
They clearly belong to the enzymes or factors, although commonly 
not hereditarily transported. But the further discussion of this point 
must be deferred to later. 
The only place in literature, hitherto come to my knowledge, 
where an hypothesis is indicated somewhat corresponding to my 
view, is to be found in Barsson. He says ?): ‘‘Ueber die physika- 
lische Natur der Erbeinheiten können wir noch nichts aussagen; die 
Folgeerscheinungen ihrer Gegenwart sind aber in so vielen Fallen 
1) R. P. van Catcar, Voordrachten over algemeene biologie, Pag 182 and 188, 
Leiden 1915. 
2) W. BaresoN, MENDEL’s Vererbungstheorien, Pag. 269, 1914 (Translation 
of the English edition of 1909). 
