326 PROTECTIVE INOCULATIONS. 
animal immune against Rothlauf contains an immunizing substance. I 
further ascertained that this substance is found only in the blood serum, and 
not in the solid portions of the body organs, etc., and with the exception of 
the blood was found only in the secretions of serous membranes. I also 
found that the immunizing substance is only to be found for a certain time 
after renewed infection in the immune animals, and that it gradually disap- 
pears, without the loss of immunity in the animal, however. Finally, I dis- 
covered that the animals into which one injects blood serum from immune 
animals do not acquire a lasting immunity, but are only immune for a rela- 
tively short time.” 
In experiments made in 1898 and 1894, with a view to producing 
immunizing serum for protective inoculations on a large scale, Lorenz 
met with some disappointments; but he proposes to renew his attempts 
and hopes to avoid the difficulties which have been brought to light 
by experience, one of which he states as follows: 
‘When an animal already immunized against Rothlauf receives an in- 
jection of a considerable quantity of a culture of the bacillus, in order to 
cause the production in its blood of a serum of high therapeutic value, the 
animal bears these injections without any notable reaction. But its blood 
serum contains during the following days, besides the immunizing substance, 
-also poisonous substances, and blood ‘which is taken too soon (twenty-four 
hours) after the injection has a toxic action upon animals which are already 
infected. If this poisonous serum is injected into a mouse which has been 
infected two days before with Rothlauf bacilli, in the dose of about 0.05 cubic 
centimetre, death occurs in a few hours, even when scarcely any evidence of 
sickness had been observed before the injection.” 
The fact that mice infected with this bacillus may be cured by in- 
jecting into them blood serum from an immunized rabbit has also 
been demonstrated by F. Klemperer (1892). In his experiments with 
the bacillus of mouse septicemia, and with Friedlander’s bacillus, he 
found that serum from an immune rabbit may be used to immunize 
mice and also to cure them after infection, while serum from a non- 
immune rabbit has no such action. The immunity produced in this 
way was found to be specific. That. is, animals immunized against 
the pathogenic action of one of these bacilli were not protected against 
infection by the other. The “ Heilserum” when added to cultures in 
vitro did not prove to have any special bactericidal action. 
HYDROPHOBIA. 
Notwithstanding the extended researches made, especially in Pas- 
teur’s laboratory, the etiology of hydrophohia still remains unsettled. 
It has been demonstrated by experiment that the virus of the disease 
is located in the brain, spinal marrow, and nerves of animals which 
have succumbed to the disease, as well as in the salivary secretions 
of rabid animals; and that the disease may be transmitted by intra- 
venous inoculation, or by introducing a small quantity of virus beneath 
