16 
Transactions Texas Academy of Science.— 1907. 
“phagocytes.” This theory has been strenuously attacked to such effect 
that Metschnikoff has been forced to admit that the phagocytes are not 
the sole agents of bacterial destruction, but that the fluids of the body, 
particularly the blood serum, possesses this power to a marked degree. 
Yet he persistently affirms, and supports it with proof, that this par- 
ticular quality of the blood serum is derived from phagocytes, which 
part with their digestive substance by undergoing solution in the serum 
(phagolysis) . 
As we have no space to enter into a prolonged discussion of this sub- 
ject, it may suffice to say that probably phagocytosis does not play such 
a prominent primary part in the destruction of organisms as was once 
thought, ,but plays rather a secondary one in giving the final coup de 
grace (Lazarus-Barlow) , when the anti-bacterial and antitoxic sub- 
stances have rendered the organisms less formidable and less toxic. 
The study of the effects of soluble toxins carries us into the very 
heart of the question. Even when the tissues are apparently fighting 
living bacteria., they are in reality fighting the toxins the bacteria are 
manufacturing; and, although the bacteria may be destroyed and di- 
gested, their toxins may yet be so poisonous as to destroy life. It is 
probably true that many toxins play the part of chemical compounds, 
which are harmful to protoplasm, without combining with it strongly. 
These are easily divorced from their combination and excreted from 
the body by means of the kidneys. But other poisons form strong com- 
binations with protoplasm, so strong in fact, that divorce is difficult 
and often impossible. As an example of a weak combination, we may 
cite the toxin of diphtheria ; as an example of the strong, that of tetanus. 
These combinations of toxins and protoplasm have often been graph- 
ically represented by the benzene ring, where the loosely attached atoms 
of hydrogen can be replaced by the toxin. Bui this method, although 
it gives us a mental picture of combination, gives us no insight what- 
ever into the exact nature of the union. We know so little of the accu- 
rate chemical formulae of toxins that we are absolutely unable at pres- 
ent to express satisfactorily their combinations with the complicated 
albuminous compounds. 
The most philosophical explanation of these combinations yet pre- 
sented to us is the theory of Ehrlich, in which he has represented dia- 
grammatically the changes which occur in protoplasm when brought 
into chemical contact with toxins. Earlier in this paper while describ- 
ing the bactericidal power of serum it was mentioned that it could be 
increased to a high degree by injecting into the blood of animals toxins 
produced by bacteria; and, further, that the bactericidal power could 
be increased in a particular direction by injecting the poison of a par- 
ticular species, so that finally the serum would become intensely de- 
