THE COMMUNICABLE DISEASES 519 
procedure for the discovery of the existence of tubercu- 
losis — the use of tuberculin in one of its forms by one 
of its methods of application. The use of this test 
in veterinary medicine needs no commentary, having 
made its place in clinical and hygienic practice for a 
quarter century or more. Armed wdth the knowledge of 
the satisfactory use of the toxins of tubercle bacillus in 
cows, Dr. Penrose, Dr. C. Y. White, Dr. A. E. Brown and 
Dr. Leonard Pearson began in 1901 a series of experi- 
ments with old tuberculin of Koch which have led to the 
development of a technique for its use in the detection 
of infected monkeys. These interesting and instructive 
animals, being kno^vn as highly susceptible since most 
of the collection died of the disease in those days, and 
being handled with reasonable ease by experienced men, 
were investigated as the most important specimens upon 
which to perfect the method. Other varieties have been 
studied since and I shall refer to them individually. The 
greatest amount of work and the most conspicuous suc- 
cess attended the observations upon monkeys and the 
results of this study are now in daily use in this Garden. 
The work, conclusions and results, originated by 
Doctor Penrose, Doctor White, and Doctor Brown 
can be described as one of the most completely satis- 
factory series of observations in scientific medicine. 
Applying the principle that a tuberculous animal reacts 
to the injection of tuberculin by a temperature rise, 
the normal temperature curve of the monkey was studied, 
that of the tuberculous monkey determined by killing 
many specimens. This enabled them to state which 
animal was infected, wliich was not and to place on exhibi- 
tion only healthy specimens. Added to this, strict hj^gi- 
enic principles in the housing and handling of the animals 
have resulted in the elimination of the disease from our 
exhibition house. Occasionally a case may develop, per- 
haps from feeding by risitors, but the matter is no longer 
a problem. I know of no more complete and satisfactory 
