122 GLANDERS AND FARCY. 



specitic infectious diseases, there exists in glanders a period of 

 quiescence, so to speak, between the reception of the poison 

 and the development of the characteristic symptoms. There 

 is, however, in this disease in the horse a most wonderful dis- • 

 parity, if we are to depend on the correctness of statements 

 made, in the duration of the incubative period — a disparity 

 utterly irreconcilable, considering the natural history of specitic 

 infectious diseases — if no regard were had to defective or im- 

 perfect observation, which, in the circumstances of such cases, 

 cannot be remedied. 



When resulting from direct inoculation, it is usually from 

 four to seven days, or even more. When following the 

 normal mode of propagation, that of infection, mediate or 

 immediate, it is somewhat longer ere the diagnostic symp- 

 toms are developed. In these cases an interval of several 

 weeks, or even months, is said occasionally to elapse between 

 the reception of the morbific agent and the ap^Jearance of 

 characteristic symptoms. 



In all probability such lengthened periods of incubation do 

 not actually occur, but may be accounted for very simply, if 

 wc arc to regard it as certain, or at all probable, that the 

 reception of the glander virus as a volatile agent acts primarily 

 on the blood and internal viscera, and that this contamina- 

 tion and induction of specific organic changes in the lungs, 

 trachea, and upper air-passages, does not for long interfere 

 with the enjoyment of apparent good health and activity, and 

 that the symptoms which at last diagnose the disease are of 

 secondary importance ; or if local lesions have, at the period 

 of the reception of the virus, been produced, they have shortly 

 afterwards healed, the contamination of the system moving 

 slowly but steadily on, until subsequently the local lesions by 

 which the disease is recognised are established. 



During the latent period of the disease, certain conditions, 

 if brought to bear on the animal so circumstanced, seem to 

 have a power of hastening the development of the diagnostic 

 symptoms. Long-continued, or rapidly performed work, and 

 other adverse conditions such as placing animals in unhealthy 

 stables, exposure to cold and damp, with insufficient food, 

 have all been noted as operating in this manner. Indeed, so 

 well has it been understood that any sudden change, sanitary 



