CLINICAL EVIDENCE OF VALUE OF SERUM 467 



about the yards. It would seem in these cases, as in the case of the 

 pigs mentioned in the herd which formed the basis of this eighteenth 

 experiment, that the giving of even the double treatment during 

 the period of pregnancy does not result in the development of an 

 immunity in the pigs which are at that time in the uterus of the 

 mother. On the other hand, if these same sows are again bred and 

 allowed to bring forth a litter of pigs, this second litter will have an 

 immunity which lasts up to about the time of weaning. 



As a matter of interest, I recall an unusual case reported by Dr. 

 Balser, of Newcastle, Indiana, in which he gave a pregnant sow the 

 double or simultaneous injection, and a few weeks later the sow 

 gave birth to a litter of hving pigs which were suffering from cholera 

 at the time of birth. The question arises. Were these pigs infected 

 while in the uterus of the mother by the injection of the virus 

 used in giving the double treatment? I think not. I think it more 

 likely that the mother of these pigs was, in reality, developing an 

 attack of cholera at the time the treatment was given. While 

 there may have been no visible signs of the disease at that time, I 

 think the germs of cholera were already in the body of the sow and 

 that she was undergoing the incubation period. 



The injection of the double treatment was sufficient to check the 

 progress of the disease in her body, but was not able to reach the 

 virus, which had probably already penetrated to the circulation 

 in the uterus and had reached the unborn pigs. As a result, the 

 mother did not develop an attack of cholera, but the pigs were not 

 reached by the injection, and they went ahead and developed the 

 disease, being born with it. 



The results following injection of pregnant sows at serum plants 

 not only with small doses of virus, such as are used in giving the 

 double treatment, but also later on with doses of over one thousand 

 times this size, without the production either of abortion or signs 

 of disease in the pigs, is pretty strong evidence that it is not pos- 

 sible or, at least, not likely for the disease to be caused in this 

 manner. 



Herd Number Nineteen. — The herd which is reported as the 

 nineteenth in this series of experiments was located in the south- 

 west quarter of Section 36, Milford Township, Story County, Iowa. 

 This farm was located only about three-quarters of a mile from 



