84 VACCINE AND SEEUM THEEAPY 



dividuals of the same morphological species. The 

 prevalence of disease in new-born animals caused by 

 the colon group of bacteria may perhaps be accounted 

 for by the fact that the serum of new-born animals 

 does not contain any free antibodies for these organ- 

 isms, whereas in older animals the serum does. 

 Thus the normal serum of an adult animal will 

 agglutinate this bacillus in dilutions of 1 : 10 or 1 : 20 

 — a phenomenon possibly referable to its habitual 

 presence within the body. 



On account of the strict specificity of each strain of 

 the colon bacillus, it is extremely difficult to prepare 

 a serum or vaccine containing universal immunising 

 properties against this group ; also, as the disease is 

 commonly caused by other varieties of bacteria, it 

 makes the preparation of such serum or vaccine for 

 practical purposes still more difficult. However, an 

 immune serum of a polyvalent character has been 

 prepared by Jensen, and, according to this author, 

 very satisfactory results have been obtained from its 

 use. Mixed bacterins are now commonly in use, 

 prepared from the B. coll communis, paracolon 

 bacillus, and the B. ahortus. According to statistics, 

 very favourable results have been recorded from the 

 use of both the serum and vaccine. The serum 

 should be given in doses of 20 to 30 c.c. immedi- 

 ately after birth to animals born on infected premises. 

 As a curative, where the disease has appeared, from 

 50 to 100 c.c. should be given. The passive immu- 

 nity so established may be prolonged by the subsequent 



