294 PROTECTIVE INOCULATIONS. 
diphtheria. It is precipitated by alcohol, acids, and by magnesium 
sulphate. 
Finally, Westbrook, in a still more recent research (1894), arrives 
at the conclusion that the cholera spirillum produces various toxic’ 
proteids which in small amounts produce immunity in susceptible 
animals, and the production of which depends to a certain extent 
upon the culture medium; or that its toxin is a substance of constant 
chemical composition which is mixed with various albuminous sub- 
stances, either contained in the culture medium or developed in the 
culture. Duclaux is of the opinien that the last supposition is cor- 
rect, and that the so-called toxalbumins are not bodies of definite 
chemical composition, but mixtures of toxins and albuminous sub- 
stances. 
Experiments made upon the lower animals show that the intro- 
duction of these cholera toxins into the body of a susceptible animal, 
either with or without the living cholera spirillum, results in the 
establishing ci a certain degree of immunity against the toxic action 
of cholera cultures. And there is good reason to believe that a non- 
fatal attack of cholera in man gives the individual a relative immunity 
from subsequent attacks, for sometime at least. This has led to ex- 
tended experiments with reference to the possibility of producing a 
similar immunity in man by means of protective inoculations. The 
experiments bearing upon this point which have been made upon the 
lower animais will first engage our attention. 
Hueppe (1887) first demonstrated the fact that injection of a small 
amount of a cholera culture into the peritoneal cavity of a guinea-pig 
is fatal to these animals. 
In the following year (1888) Gamaleia reported his success in in- 
fecting guinea-pigs by subcutaneous injections of blood from an in- 
fected pigeon. He found that by successive inoculations in pigeons 
a considerable increase in virulence is established; and that while 
guinea-pigs were not fatally infected by subcutaneous inoculations 
with ordinary cultures, they invariably died when inoculated with the 
more virulent culture in the blood of an infected pigeon. Also, that 
when guinea-pigs were inoculated with ordinary cultures, or with 
cultures sterilized by heat, they were subsequently immune, and re- 
sisted inoculations with the most virulent material. In the same 
year the author referred to announced the discovery of a spirillum 
which closely resembles the cholera spirillum—his “ Vibrio Metch- 
nikovi.” This was obtained from the intestinal contents of fowls 
suffering from a fatal infectious ‘malady (in Odessa). According to 
Gamaleia, chickens and pigeons which have survived an inoculation 
