ANTIDYSENTERIC SERUM 247 



In this instance the minimal lethal dose was 0.2 c.c. and subsequent 

 cultures of the same strains, grown under similar conditions, showed this 

 dose to remain quite constant. 



It is good practice to keep the cultures growing during the entire 

 time of immunization. Cultures may, however, be grown for three 

 weeks, filtered through porcelain, and with the addition of 0.5 per cent, 

 phenol, the toxin preserved for long periods of time. The minimal 

 lethal dose of such a toxin is determined in the manner directed -above. 



Immunizing the Animals. Since horses are quite susceptible, the 

 initial dose of unfiltered and unheated culture should not be larger 

 than the minimal lethal dose for a young rabbit. The dosage is grad- 

 ually increased, and the injections are given subcutaneously for from 

 four to six months, after which several injections of from 300 to 350 c.c. 

 may be given intravenously at one time. If at any time diarrhea and 

 other symptoms of toxemia are well marked, subsequent doses should 

 be smaller and should be given at longer intervals until a higher immu- 

 nity is produced. 



Instead of using bouillon cultures, young agar cultures may be used, 

 the bacilli being grown for seventy-two hours, and one-tenth of an ordi- 

 nary slant being given as the first dose. The early doses are heated to 

 60 C. for an hour and injected subcutaneously; the later doses consist 

 of cultures washed from 30 to 40 tubes, and are given intravenously. 



Flexner and Amoss Method for Rapid Production of Antidysenteric 

 Serum. 1 By this method potent antidysenteric sera can be safely 

 prepared in the horse by the method of three successive intravenous 

 injections of living cultures or toxin with intervening rest periods of 

 seven days; and effective serum for therapeutic purposes may be pre- 

 pared in about ten weeks. By inoculating alternately living bacilli 

 belonging to the Shiga and Flexner groups a polyvalent serum of high 

 titer may be secured which should be suitable for the serum treatment 

 of acute bacillary dysentery, irrespective of the particular strain or 

 strains of the dysentery bacillus causing the infection. 



Cultures are grown upon agar-agar slant surfaces in tubes 15x160 

 mm. in size for twenty-four hours, and the growth in each tube suspended 

 in 2 c.c. of salt solution. Horses are injected intravenously; -the first 

 dose is 1 c.c. of the suspension of Flexner bacilli after heating to 

 60 C. for thirty minutes; on each of the following two days 5 c.c. of 

 heated suspension are usually given, followed by a rest of seven days, 

 when living cultures are^ injected. The temperature is taken daily and 

 1 Jour. Exper. Med., 1915, 21, 515. 



