PROTECTIVE INOCULATIONS. 317 
time must be allowed to elapse between the injections for the complete recov- 
ery from the general and local effects. As the quantity of the toxins is in- 
creased the general effects generally decréase, perhaps a rise of a degree for 
twenty-four hours. The local effect partakes more of an cedema, and has the 
character of an inflammation. 
‘At a certain stage, usually after two months’ treatment, when fifty to 
sixty cubic centimetres can be injected without harm, there is no general re- 
action, but a large cedema at the site of the injection, which disappears 
within from twenty-four to forty-eight hours. Toward the last, even when 
two hundred to three hundred cubic centimetres are given, there is only an 
enormous cedema, which disappears within from twelve to eighteen hours. 
When these inordinately large quantities can be given with only a local re- 
action being manifest, the horse has come well under the influence, and the 
blood will be found to be rich in the antitoxin. 
‘‘There is a curious fact well worth noting: At the end of the second 
month of treatment, when the horse can bear as much as fifty to sixty cubic 
centimetres of the toxins without discomfort, the blood will be found to con- 
tain but little of the antitoxin. The antitoxin only appears after repeated 
stimulation of the cells (?) by the large and frequent doses of the toxins.” 
The subcutaneous injections do not yield a serum as rich in the 
antitoxins as when the toxins are injected directly into the blood cur- 
rent. When it is desired to do this, toward the last of the treatment 
the toxins are injected directly into the jugular vein. The process is 
tedious and requires a longer time, and for practical purposes has not 
been found so satisfactory as the simple subcutaneous injection. The 
strength of the serum is tested by using young guinea-pigs of five 
hundred grammes weight. One gramme of the serum usually will 
protect fifty thousand grammes of guinea-pig against a fresh virulent 
culture of the Bacillus diphtherwe. This is the strength that is used 
in the hospitals. By the intravenous injections a serum of the pro- 
tective strength of 1:100,000 can be obtained. 
When fully immunized from six to eight litres of blood may be 
taken from a horse at one time, but as a rule it is better not to take 
more than three. The blood is drawn from the jugular vein, by means 
of a small trocar and cannula, into wide-mouthed bottles having a ca- 
pacity of 2.5 litres; these are placed in an ice chest for twenty-four 
hours to give time for the separation of the serum, which is then 
transferred to smaller receptacles for preservation. 
The dose of serum prepared in this way, when used to protect from 
diphtheria infection, is five cubic centimetres for a child under ten 
years of age, and ten cubic centimetres for older children. This does 
not afford an absolute protection, but is believed to be generally 
effective, and in case of failure the attack is said to be of a mild 
character. The curative dose of Roux’s serum is twenty cubic centi- 
metres for children, and thirty to forty cubic centimetres for patients 
over fifteen years of age. The larger dose is divided and given, at 
the same time, by subcutaneous injection in two places. Antiseptic 
