292 
Transactions of the Royal Society of South Africa. 
" strain 2 " ; normal horse serum injected subcutaneously in back at 
same time. 
1. B. diphtheriae+'lO c.c. unheated serum 
2. 
3. 
*4. 
*5. 
no serum .... 
+ 10 c.c. serum, 57° C, 1 hr. . 
+50 c.c. of a serum dilution, 
1 part in 5 of normal saline, 
heated at 70° C, J hr. 
+ 60 c.c. of a serum dilution, 
1 part in 5 of normal saline, 
heated at 90° C. \ hr. 
+50 c.c. of a serum dilution, 
1 part in 5 of normal saline, 
heated at 100° C. for 5 
minutes .... 
survived, 
died 2nd day. 
survived. 
died 2nd dav. 
died 2nd day. 
died in 24 hours, 
showing more mark- 
ed lesions than other 
animals ; marked 
haemorrhagic in- 
flammatory oedema 
at site of inoculation, 
with marked 
haemorrhages in 
suprarenals, lungs, 
and intestinal wall. 
Experiments with Rabbits. 
Using rabbits as the test animal, horse serum was found to exert the same 
protective action against B. diphtheriae as in the case of guinea-pigs ; the 
particular effect was not therefore limited to B. diphtheriae infection in 
one species of animal only. Table IV exemplifies one of these experiments. 
Table IV. 
Rabbits of equal weight injected subcutaneously with 4 c.c. of a 3-days 
bouillon culture of B. diphtheriae, " strain 3." 
1. +20 c.c. normal horse serum injected 
subcutaneously at different site . survived. 
2. No serum ...... died 3rd day. 
* The serum was diluted to prevent coagulation on heating. 
