Natural Infection. 685 



develops only in exceptional instances as a result of inhalation 

 of the infection; this mode of infection can be assumed only 

 when the morbid process manifests itself exclusively in broncho- 

 pneumonic foci. An infection after this manner can in fact 

 occur only through the medium of fresh particles of secretion 

 that are forcibly expelled from the lungs in the act of sneezing 

 or snorting; dried virus loses its virulence or vitality within a 

 very short time. 



The air uormally expired by glandered horses is not infectious. This ia at 

 least the conclusion reached in their experiments by Eenault, Cadeac & Malet. 

 The latter investigators forced healthy horses to inspire the same air that was 

 expired by glandered horses by means of linen tubes passing from the head or nos- 

 trils of one animal to the other, but in no instance did they observe the transmis- 

 sion of the disease to the healthy animals. They also failed to produce the disease 

 by the subcutaneous injection of the precipitate of moisture from the expired air 

 of glandered horses. On the other hand Nocard failed to get positive results in 

 any case where he injected virulent cultures, that had been admixed with albumin- 

 ous substances and dried without the application of heat, into the peritoneal cavity 

 of guinea pigs, or where he blew the dried material into the nostrils of asses. 

 Similarly, Hutyra found that virulent nasal secretion, dried either in the presence 

 of light or in complete darkness, was ineffective in producing glanders by insuffla- 

 tion in horses. Finally Cadeac & Malet report positive results from intratracheal 

 injections of 10 to 20 cc. of virulent cultures in asses in only 50% of the cases. 



The disease may also be produced experimentally by infection 

 through other uninjured mucous membranes. Thus guinea pigs may 

 be infected by the application of a few drops of culture on the con- 

 junctiva or the mucous membrane of the vagina (Galtier). Under 

 natural conditions this mode of infection can of course be only of rare 

 occurrence (Richter observed primary glanders of the conjunctiva of 

 the horse and it is recorded that a Russian stallion transmitted the 

 disease to a number of mares in Prussia by coitus). 



A severance of continuity of the skin or at least of its horny 

 epithelial layers is, as a rule, necessary before infection can 

 occur. The domestic animals are, however, well protected 

 against this possible mode of infection, since infectious secre- 

 tions usually adhere to the hair coat, dry up and become harm- 

 less. This explains why primary cutaneous glanders is gen- 

 erally of rare occurrence as compared with metastatic affection 

 of this organ. As a rule the virus is rubbed into lesions of the 

 skin by means of the harness or combs and brushes previously 

 used on affected horses, or infection may take place through 

 larger cutaneous wounds, or through bites (Lothes). 



Babes observed the development of the disease in guinea pigs following rub- 

 bing of virulent cultures into the previously shaved skin, as had also been observed 

 long before by Viborg. However, when Nocard repeated the experiment with asses 

 and 15 guinea pigs he obtained positive results in only three of the guinea pigs. 

 Probably the infection was in all cases brought about through abrasions in the 

 superficial layers of the skin, but nevertheless the possibility that the bacilli may 

 pass through the hair follicles of the intact skin and from these into the neighbor- 

 ing lymph spaces, can not be excluded. 



The disease is usually introduced into uninfected stables 

 through the medium of affected horses. As a rule the horses 



