MODE OF SPREAD 323 



gain entrance to the blood stream, they soon settle in the various 

 tissues and organs. Accordingly, even in acute cases it is usually 

 quite imposible to detect the bacilli in the circulating blood, 

 though sometimes they have been found. It is an interesting 

 fact, shown by observations of the disease both in the human 

 subject and in the horse, as well as by experiments on guinea- 

 pigs, that the mucous membrane of the nose may become infected 

 by means of the blood stream another example of the tendency 

 of organisms to settle in special sites. 



Mode of Spread. Glanders usually spreads from a diseased 

 animal by direct contagion with the discharge from the nose or 

 from the sores, etc. So far as infection of the human subject 

 goes, no other mode is known. There is no evidence that the 

 disease is produced in man by inhalation of the bacilli in the 

 dried condition. Some authorities consider that pulmonary 

 glanders may be produced in this way in the horse, whilst others 

 maintain that in all cases there is first a lesion of the nasal 

 mucous membrane or of the skin surface, and that the lung is 

 affected secondarily. Babes, however, found that the disease 

 could be readily produced in susceptible animals by exposing 

 them to an atmosphere in which cultures of the bacillus had 

 been pulverised. He also found that inunction of the skin 

 with vaseline containing the bacilli might produce the disease, 

 the bacilli in this case entering along the hair follicles. 



Serum Reactions. Shortly after the discovery of agglutination in 

 typhoid fever, McFadyean found that the serum of glandered horses 

 possessed the power of agglutinating glanders bacilli His later observa- 

 tions show that in the great majority of cases of glanders a 1 : 50 

 dilution of the serum produces marked agglutination in a few minutes, 

 whilst in the great majority of non- glandered animals no effect is 

 produced under these conditions. The test performed in the ordinary 

 way is, however, not absolutely reliable, as exceptions occasionally occur 

 in both directions, i.e., negative results by glandered animals and positive 

 results by non-glandered animals. He found that a more delicate and 

 reliable method is to grow the bacillus in bouillon containing a small 

 proportion of the serum to be tested. In this way he obtained a distinct 

 sedimenting reaction with a serum which did not agglutinate at all 

 distinctly in the ordinary method. Within recent times the sedimenta- 

 tion test by the ordinary method (p. 121) has been most generally used. 

 The general result seems to be that distinct sedimentation within thirty- 

 six hours with a serum dilution of 1 : 1000 may be taken as a positive 

 result, indicating the presence of glanders ; whilst reactions with dilutions 

 between this and 1 : 500 are highly suspicious but not conclusive. The 

 deviation of complement test (p. 131) is also applicable in the case of 

 glanders, and this has given valuable results in the hands of various 

 observers. Precipitin reaction may also be obtained on the addition of 

 mallein or an extract of the glanders bacillus to the serum of a glandered 

 animal. These reactions, which of course depend on the presence of anti- 



