48 
Tizzoni believes that the weakening of the dried precipitated 
toxin is due to the production of an acid substance. It was for this 
reason that Knorr dissolved the precipitate in a 10 per cent solution 
of sodium chloride. 
Tizzoni at one time believed the instability of the precipitated 
toxine to be due to the ammonium sulphate which remained in the 
precipitate and eliminated this by spreading the fresh moist pre- 
cipitate upon porous porcelain; but the toxine so obtamed showed 
itself to be no more stable than those that preceded it. On the 
other hand, he obtained ver}^ satisfactory results by the elimination 
of the sulphate of ammonium by means of dialysis. Tizzoni claims 
that tetanus toxine does not dialyze. He recognizes that the sta- 
bility of the toxine so prepared is not indefinite, for he states that 
this dialyzed precipitate passes through some modification in the 
course of time. The toxine, however, is sufficiently stable for the 
purpose of standardizing antitox.in and for scientific tests. Besides 
serving for the preparation of the standard antitoxm, this method 
is applicable for concentrating the poison for injection into animals. 
Tizzoni showed further that almost all of the toxines produced by a 
culture are precipitated by ammonium sulphate — that is, there is 
very little loss in this process. 
Tizzoni found that antitoxic serums measured against fresh tetanus 
toxine and an old and weakened poison gave different results. He 
believes that this is due largely to the modified toxine or “toxoid” 
contained in the weakened, serum. 
Tizzoni considers it of importance to use for the preparation of 
the toxine, cultures which at the period of their greatest develop- 
ment contain the greatest degree of toxicity. Thus 0.001 c. c. of 
the filtrate should constantly kill 1 kilogram of rabbit in four days. 
Cultures which at the moment of precipitation with sulphate of am- 
monium do not possess this toxicity are rejected. 
In view of the differences shown by different species of animals 
Tizzoni always uses the rabbit for standardizing both toxine and 
antitoxin, and finds it necessary to take into account the weight of 
the animal. He concluded that the principal condition to be real- 
ized in the standardizing of tetanus antitoxin is the possession of a 
stable toxine. He dwells upon the importance of determining the 
therapeutic value of the serums in relation to the antitoxic value 
as determined by anhnal tests. Too much confusion prevails to-day 
in the method of representing the value of tetanus antitoxic serums. 
This condition should be terminated by adopting a language common 
to all and easily understood. In the present state of affairs the con- 
fusion has. arrived at such a point that anyone concerned in a dis- 
cussion can not judge from the value attributed to two serums of 
