174 
Dourine 
The seven sera, Nos. 1-7, used in this experiment are taken from 
dourine control horses in the first, second, third, fourth, fifth, sixth and 
seventh year of the disease, respectively. No. 1 from a mare showing 
clinical symptoms; No. 2 from a stallion showing occasional symptoms; 
Nos. 3 and 4 from mares very rarely showing symptoms and progressing 
towards recovery; Nos. 5, 6 and 7 from mares that have not shown 
any symptoms for three, four and five years respectively, and which 
have made complete recovery, been bred to a healthy stallion each 
year—without transmitting infection—and raising healthy offspring. 
In addition to the above, among our experimental horses that have 
recovered from dourine, there are two mares that give a positive 
(+ + + +) reaction with 0-2 c.c. serum after six years, and one mare a 
positive (+ + +) after seven years. On the other hand, there are three 
mares that have entirely ceased to react, even with twice or three times 
the amount of serum, after six to seven years of recovery, although 
they reacted positively up to the fifth year. 
Conclusion. 0-2 c.c. of horse serum from a dourine infected animal 
contains up to forty units of specific antibody. In the case of horses 
that have completely recovered from dourine and which are no longer 
able to transmit the disease, one or several units of antibody are present 
in the same amount of serum up to the fifth year of recovery. After 
that period thay may cease to react—indicating that not only was an 
absolute recovery made but that the immunity was lost in about five 
years (proof of which has been given by inoculation experiments with 
T. equiperdum on recovered horses). 
For diagnostic tests it is sufficient to use three doses of serum, 
namely, 0-2, 0-15 and 0-1 c.c. 
The first appearance of a positive serum reaction in dourine 
infections. 
Having fixed upon a standard dosage of suspected serum, it is now 
necessary to know the incubation period of dourine and when a first 
positive serum reaction may be expected, for otherwise a negative 
reaction would be valueless or even misleading. 
In this connection there follow the records of some experiments: 
