s 
As will be seen from the details of the work which follow, I failed 
to propagate the disease from rat to rat. 
This feeble power of the infection to spread from rat to rat is a 
decided limitation to the virus as far as its practical application is con- 
cerned. It is easy enough to make the rats in a cage eat the cultures 
soaked in food, but in a wild state this would not be so easy, and if only 
the rats that eat the virus die, there is little advantage over phosphorous, 
arsenic, and other chemical poisons. 
It is not considered necessary to give in full detail all the experiments 
made with the virus. A few of the more striking ones follow. 
No. 1. SEVENTY EATS FED ON CULTURES IN INCREASING AMOUNTS. 
Seventy white and gray rats were fed April 8 with 4 agar slants I 
(original) of Danyz’s virus No. 2, obtained direct from the Pasteur ^ 
Institute. The cultures were shaken up with water and soaked on dry 
bread, according to the instructions. The agar itself was also fed to the j 
rats. They ate it all up greedily, food having been withheld for a day 
previously — i 
Died. 
Twelve days after feeding 
Fourteen days after feeding 
Thirty days after feeding 
Thirty-one days after feeding. . . 
Thirty-two days after feeding... 
Thirty-three days after feeding 
1 I 
2 j 
1 i 
1 i 
1' ' 
1 ; 
Total 7 1 
I 
Seven of the 70 rats died. One of the 7 died of a peritonitis, due ; 
to a long nonmotile bacillus which had no resemblance to the organ- ; i 
ism that was fed to the rats. The others died of a disease evidently ! j 
due to the ingestion of the cultures. | 
In most of the animals the small intestines were found to be the seat ! I 
of inflammation with enlargement of the lymphatic glands. The spleen i | 
and liver showed little change. The lungs were often the seat of con- I 
gestion and hemorrhagic inflammation — sometimes infarct. The inges- 
tion of the virus causes a local reaction in the intestines, followed by i 
an invasion of the organism into the blood, producing a septicaemia. 
The surviving rats, remaining perfectly well to all appearances, were 
again fed with a fresh culture of the virus. They were now divided > 
into 4 lots and fed with variable amounts in order to determine ; 
whether the small quantity ingested produced an immunity and 
whether the effect is proportionate to the amount eaten. 
THIRTY -THREE EATS EE FED WITH LARGE QUANTITIES OF BOUILLON , 
CULTURES. 
On May 16, after two days’ starving, 33 of the surviving rats of expert- ( 
ment No. 1 were given a liter of a young bouillon culture. One-half of i 
this was given as drink, the other half soaked on dry bread. The rats 
