MODE OF SPREAD 313 



nective-tissue growth is present in proportion to their age. The 

 tendency to spread by the lymphatics is always a well-marked 

 feature, and when the bacilli gain entrance to the blood stream, 

 they soon settle in the various tissues and organs. Accordingly, 

 even in acute cases it is usually quite impossible 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 showed that the serum of glandered horses 

 possessed the power of agglutinating glanders bacilli. His later observa- 

 timis 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 

 \\.iy 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 

 sediuienting 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. 120) 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 

 ln'twcen this and 1 : 500 are highly suspicious but not conclusive. The 

 deviation of complement test (p. 130) is also applicable in the case of 

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

 observers ; a precipitin reaction mny also be obtained on the addition of 



