SCIENCE AND INDUSTRY. 
= 
Even after culture through many generations on- artificial media, the 
organism can be used to infect other animals Although the disease naturally 
attacks only the cow, yet the females of most of the domesticated animals cat 
be infected and abortion induced in them. Of the small experimental animals 
the guinea pig is readily infected, and’ inoculation’ of this’ animal provides 4 
very useful method of obtaining a pure culture from contaminated or sparsely 
infected material. If such material be injected into the peritoneal cavity 0 
the guinea pig the animal usually suffers no apparent inconvenience, but if 
killed in four or five weeks’ time will be found to have a slightly enlarged 
spleen,-from which pure cultures of the abortion bacillus can be obtained. 
But this line of proof is strongly supported by certain biological tests, which 
can be applied to a cow suspected of being infected with the disease. It is 
common knowledge that for the diagnosis of typhoid fever in man a small 
sample of blood is taken from the patient for testing. The test depends of 
the fact that when a man or an animal is attacked by the micro-organisms of @ 
disease, the blood of the man or animal proceeds to manufacture munitions of 
defence, which accumulate in the blood, and can be detected there. Among 
many others, some substances called “agglutinins” are commonly formed, and 
these have the peculiar property of crowding together, or clumping, or agelutin 
ating, the specific bacteria responsible for the particular disease when such 
organisms are suspended in a fluid. Thus a liquid culture or other uniform 
suspension of the typhoid bacillus, if examined in a hanging drop under the 
microscope, is seen to be crowded with freely movable organisms, hurrying and 
scurrying in all directions. If to such a preparation a minute quantity 0 
blood from a person affected or recently recovered from typhoid fever is added; 
and the result observed under the microscope, it will be noticed in the course 
of a few minutes that there is a tendency for the bacilli to congregate into small 
groups and at the end of an hour the field shows a number of sucli 
clumps with clear spaces between them, and no freely moving bacilli. With @ 
similar quantity of the blood of a normal person no agglutination) or clumping 
would take place, a so ‘the test is of diagnostic value. 
A similar test can be applied in many other diseases, and McFadyean and 
Stockman in London showed its value in relation to contagious abortion 0 
cattle. In this case, however, the test is performed in a somewhat different 
manner. Into each of a number of small test tubes is put an equal quantity 
of a faintly hazy suspension of the abortion bacillus. Amounts of blood seru™ 
of a suspected cow are now added, commencing with, say, 1-10th c¢.c. in the first 
tube, then 1-20th, 1- 50th, 1-100th ce., down to 1-1000th c.c., or less in succeed” 
ing tubes. The mixture in each tube is shaken, set aside in the incubator for 
24 hours, and then the tubes are examined, If the cow is infeeted with col 
tagious abortion there will be agglutination of the bacilli in the suspensio” 
As a result the larger masses will usually sink, and leave the supernatant liquid 
quite clear, the masses forming a matted sediment. Sometimes the clearing }* 
incomplete, though clumping is evident, 
io — 
aia i. iene " ani ere 
There is sometimes some clumping with the blood serum of a normal healthy 
cow when a relatively large amount of serum, say 4 or 4 ec. has been used 
What is diagnostic of the disease, however, is the occurrence of agglutinatio® 
when only 1-100th or 1-1000th ¢.c. of serum is used in a tube. The experiment 
is controlled by the fact that tubes containing a similar suspension of the bacilli 
without the addit*»n of any cow’s serum, remain hazy and unsedimented. Fut” 
ther, the addition of similar minute quantities of serum from known unaffected 
38 
