CONTAGIUM AND MODE OF TRANSMISSION. 157 



confluent, may produce, by infiltration and other inflammatory 

 results, death of considerable portions of the cutis and sub- 

 jacent tissues, with accompanying or consequent ulceration 

 and a tardy healing process, extensive local oedema con- 

 tinuing as a troublesome sequel for some time. Unless irri- 

 tated by bits or halter-ropes being placed in the mouth during 

 the period of the eruption, the j)ustules, after discharging their 

 contents, very quickly scab over ; or where an open sore exists, 

 it is rapidly filled by healthy granulations, and in a very 

 short time is so perfectly cicatrized that no scars or indenta- 

 tions are left. 



Contagium and Mode of Transmission. — It is said by the 

 majority of observers that equine variola is only propagated 

 from horse to horse, or from the horse to other animals, by 

 direct contact ; others, however, particularly our American 

 brethren — who, from the accounts which they have published, 

 seem to see more of it than we do — believe that the virus is 

 not only fixed, but also volatile, that the disease may be trans- 

 mitted by cohabitation as well as inoculation or direct contact. 

 This is certainly what we should expect, and is in accordance 

 with what we know occurs in connection with variola in the 

 other animals which come under our care. 



What may be the exact nature of the materies morbi, 

 whether organic germs, granules, molecules, or living particu- 

 late forms, we do not know ; this, however, we are satisfied of, 

 that while some of the animal secretions seem capable of 

 transmitting the disease when implanted in the body of the 

 healthy, the most active and fruitful is the fluid from a well- 

 formed vesicle before the contained material has become 

 lactescent. How long, or under what conditions, the infecting 

 virus of horse-pox may be preserved and still retain its powers 

 of propagation when tested by inoculation, there appear no 

 reliable data upon which to form an opinion, Most probably 

 the vehicle, the vesicular fluid, when dried, may retain its 

 activity for a lengthened period, only needing favourable cir- 

 cumstances to bring its infecting powers into life. It is equally 

 probable that it may be rendered inert by such chemical agents 

 as sulphurous acid vapour, chlorine gas, carbolic acid, and by 

 its subjection to a high temperature. If we are only to regard 

 the contagium of horse-pox as a fixed and not volatile or 



