14 
G. P. No. 4502. Six c. c. antitoxic horse serum (Natl. VIII. 17) inoculated subcutane 
ously. Symptoms; recovered. 
[Previous treatment : 42 days prior, inoculated subcutaneously with 0.19 c. c. toxine No. 
7+1 unit antitoxic horse serum (Standard B27).] 
G. P. No. 4514. Two-tenths c. c. antitoxic horse serum (Natl. VIII. 17) inoculated subcu- 
taneously. Symptoms; recovered. 
[Previous treatment: 42 days prior, inoculated subcutaneously with 0.19 c. c. toxine 
No. 7+1 unit antitoxic horse serum (Standard B27).] 
SYMPTOMS CAUSED BY THE INJECTION OF HORSE SERUM INTO A SUSCEPTIBLE 
GUINEA PIG. 
Very characteristic symptoms are produced by horse serum, either 
normal or antitoxic, when injected into a susceptible guinea pig. The 
symptoms are apparently the same whether the injection is made 
subcutaneously or into the peritoneum, or whether normal or anti- 
toxic horse serum is used. In five or ten minutes after injection the 
pig manifests indications of respiratory embarrassment by scratch- 
ing at the mouth, coughing, and sometimes b} r spasmodic, rapid, or 
irregular breathing; the pig becomes restless and agitated. This 
stage of exhilaration is soon followed by one of paresis or complete 
paralysis. The pig is unable to stand or, if it attempts to move, falls 
upon its side; when taken up it is limp. Spasmodic, jerky, and con- 
vulsive movements now supervene. 
Pigs in this stage with complete paralysis may fully recover, but 
usually convulsions appear, and are almost invariably a forerunner 
of death. Symptoms appear about ten minutes after the injection 
has been given; occasionally in pigs not very susceptible they are 
delayed thirty to forty-five minutes. Only in one or two instances 
of the several hundred pigs which we have observed have the symp- 
toms developed after one hour. Pigs developing symptoms as late 
as this are not very susceptible and do not die. The chain of symp- 
toms is exceedingly characteristic. The symptoms do not always 
follow in the order given. Death usually occurs within an hour and 
frequently in less than thirty minutes. 
THE POISONOUS ACTION OF HORSE SERUM ACTS UPON THE RESPIRATORY 
CENTERS. 
Judging from the symptoms produced by the injection of horse 
serum into a susceptible guinea pig we assumed that the poison acted 
upon the nervous system. Autopsies done immediately after the 
death of the guinea pigs showed invariably that the heart continued 
to beat long after respiration had ceased. In some instances the 
heart would continue to beat a full hour when exposed. This would 
seem to indicate that we were dealing with a poison which caused 
death through the neivous control of the respiration, and the follow- 
ing experiment shows that this effect is certainly not local. 
