376 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



virus preserved with thymol and with formaldehyde for hyperim- 

 munization, as follows: 



Ten different lots of disease-producing blood were preserved with 

 one or the other of these disinfectants, and immune hogs were given 

 hyperimmunizing doses, usually by the intravenous method, after the 

 disinfectants had been in contact with the blood for from one to three 

 weeks. The formalized disease-producing blood, when injected intra- 

 venously in the usual dose for hypcrimmunization (that is, 500 cubic 

 centimeters per hundred pounds, body weight), was without visible 

 effect upon the hog, but the blood containing thymol, injected in the 

 same manner and in the same amount, proved to be distinctly toxic. 

 When employing the thymolized blood it was frequently noticed that 

 during the intravenous injection of such blood the hog would cease 

 breathing and in most cases would undoubtedly have died except for 

 the employment of artificial respiration. By great care in adminis- 

 tration and in treatment of the cases which were thus affected by 

 the thymol we were able to prevent death, and the immunes finally 

 made an uneventful recovery. 



From this work it appears that virulent blood containing sufficient 

 formaldehyde or thymol to inhibit or to destroy organisms such as 

 Bacillus suipestifer may be kept in the ice box from one to three 

 w'eeks at a temperature of G° C. and then be used for hypcrimmuniza- 

 tion without serious injury to the immunes, although it must be 

 admitted that there is a certain amount of danger to the immune hog 

 attendant upon the use of blood preserved with thymol. 



Tests to determine the potency of serum from immunes hyper- 

 immunized with this preserved virus indicate that such serum will 

 protect pigs weighing less than 100 pounds when given in doses of 

 from 15 to 20 cubic centimeters. As indicated above, the number of 

 experiments in hypcrimmunization with virus containing thymol and 

 formaldehj^de is not large, and therefore we do not consider that it is 

 absolutely demonstrated that preserved virus can be advantageously 

 used in practice as a substitute for freshly drawn virulent blood. 

 There is, however, every indication that this may be done. The 

 results thus far obtained are certainly sufficient to warrant further 

 work along this line. 



IMMUNITY IN OFFSPEING OF IMMUNE SOWS. 



Several years ago experiments were undertaken to test the im- 

 munity possessed by the offspring of immune sows. These earlier 

 tests were made by exposing the pigs after they were large enough 

 to be weaned, and they were therefore about 2 or 3 months of age 

 when exposed to hog cholera. The earlier tests resulted in showing 

 that in pigs 2 to 3 months old, from immune sows, there was no 

 regular immunity against hog cholera, although in the case of certain 

 litters there appeared to be more than the normal resistance to the 

 disease. In view of the comparatively recent observations of 

 Theobald Smith and of Anderson concerning the immunity possessed 

 by the young of female guinea pigs, which have been actively im- 

 munized by the injection of a mixture of diphtheria toxin and anti- 

 toxin, it appeared that our earlier tests might have failed to indicate 

 immunity in the offspring, because this passive immunity had pos- 

 sibly been lost during the two or three months of life before exposure 



