824 The Philippine Journal of Science 1922 
Two intradermal injections were made in the majority of the 
cases, one on the anterior surface of each forearm. On the 
right forearm the toxin was injected and on the left forearm 
the control. : 
The toxin used in our work was three years old, prepared by 
the Bureau of Science; the original minimum lethal dose was 
0.01 cubic centimeter and at the time these tests were made 
it was 0.05 cubic centimeter as determined by repeated inocula- 
tion of guinea pigs weighing from 250 to 300 grams. The test 
dose was 0.02 minimum lethal dose diluted to 0.1 cubic centi- 
meter with sterile physiological salt solution. 
The control used was either toxin overneutralized with anti- 
toxin in the proportion of 0.02 minimum lethal dose to 0.2 
unit of antitoxin, the volume of the injection being made to 0.1 
cubic centimeter by the addition of sterile physiological salt 
solution, or toxin 0.02 minimum lethal dose heated for five or 
ten minutes at 75°C. In many cases controlled by the injec- 
tion of toxin heated for five minutes, both arms showed re- 
actions, although in the control in some cases the reaction 
developed to a lesser degree, suggesting that five minutes’ 
heating was not sufficient to destroy all the toxin. In these cases 
the test was repeated, using the control toxin heated for ten 
minutes. 
The tests of the control solutions by intracutaneous injection 
in guinea pigs(7) showed reddening and cedema at the end of 
twenty-four hours at the site injected with 0.02 minimum lethal 
dose toxin heated to 75° C. for five minutes; the site of the in- 
jection of the toxin heated for ten minutes and that of the toxin- 
antitoxin mixture showed no changes, as compared with the 
cedema and necrosis produced by the intradermal injection of 
free unheated toxin. 
In our first tests no control injections were made, but three 
months afterwards those that showed reaction were retested 
with corresponding control injections. Incidentally, as was to 
be expected, we found that the first injection of toxin was not 
sufficient to confer immunity, as is graphically shown in Plate 3. 
By means of syringes graduated in hundredths, such as are 
usually employed in tuberculin injections, and fine platinum 
needles, the amount of the substance for the Schick test or the 
_control was injected slowly into the skin, between the epidermis 
and the dermal layer, which produced a wheallike swelling with 
the pores of the skin made prominent. The injections were 
easily made and fairly accurate when the needles used were 
