MODES OF PROPAGATION. 115 



into the body by means of the inspired air, or possibly by tbe 

 food or drinking-water. 



By a volatile infecting poison, it is not meant that this 

 must of necessity bejgaseons ; it need not be so : it may be an 

 organized agent, vegetable or animal, of such a character as to 

 be capable of being carried by the air to a certain distance 

 from the focus of its production. 



By this vehiclefitfmay be conveyed into the blood, first of 

 all producing a poisoned condition of this fluid, resulting in 

 the development of the peculiar and specific phenomena, the 

 tuberculation, nodulation, and distinctive lesions in different 

 situations in the lungs and air-passages, or it may at once 

 produce the specific pulmonary lesions, to be followed as a 

 sequel by general blood-poisoning. 



As so far confirmatory of the existence of a volatile infecting 

 virus are the experiments of Yiborg and of Gerlach, both of 

 whom succeeded in producing glanders in healthy horses by 

 inoculating them with the condensed exhalations and sweat 

 of the diseased. No doubt it is also true that other experi- 

 ments, such as those conducted by Hertwig and Keynault, 

 where the healthy and glandered horses were made to respire 

 at the same time through a common bag or tube attached to 

 the noses of both, were productive of negative results. 



This is perfectly possible, for we know that certain animals 

 possess a peculiar insusceptibility to the action of many 

 noxious agents, and is very httle, if any stronger evidence, 

 against the idea that the virus is volatile, and does enter the 

 system through the medium of the air, than many other 

 experiments; than that of White's, for instance, recorded in his 

 ' Compendium of the^^Veterinary Art,' in which he states having 

 retained for a considerable time in the nasal chambers of a 

 horse pieces of cloth saturated with pus from a diseased 

 animal without producing this disease. 



The great probability of the infecting agent of glanders 

 being volatile as well as fixed, and consequently its likelihood 

 of being introduced into the economy through the medium of 

 the inspired air, is] further strengthened by the fact that the 

 disease is propagated from animals which have neither dis- 

 charge from the nose nor external cutaneous lesions — nothing, 

 in fact, diagnostic, save pulmonary nodules and infiltration ; 



8—2 



