SURRA. 457 



for some time, that ulceration of the stomach, more or less exten- 

 sive, will be seen i)ost-inorte,m " (Liugard). 



NATURE OF THE DISEASE.— Surra is due to the presence, in the blood, 

 of a microbe [Tri/jKinosonia Evansi), which belongs to the animal kingdom, 

 and which lives and breeds in that fluid. This parasite always exist in the 

 blood of surra-affected horses during the frequently recurring feverish periods 

 (say, when the temperature is 103® F. or over); and surra will always ensue 

 after inoculation with blood containing it. These minute infusoria {Trypano- 

 somata) may, during an exacerbation, be. seen by the aid of a microscope, in 

 vast numbers, traversing with great activity every drop of blood examined. 

 They are said to attack and destroy the red corpuscles, and thus directly inter- 

 fere with the nutrition of the body. When the acute stage has passed, these 

 roving organisms disappear, although they leave their eggs behind them ; 

 the temperature falls ; and there is an interval of apparent health. They are 

 so tenacious of life, that, unless under special and very exceptional treatment, 

 the sufferer, after passing through a more or less prolonged course of crises 

 and intermissions (Steel has observed as many as seventeen), finally dies of 

 exhaustion, and from the diseased changes in his system, to which the disease 

 had given rise. 



Under the microscope, the presence of these parasites in a drop of blood, is 

 indicated by an irregularly intermittent and characteristic quivering of some 

 of the red corpuscles, which are much altered in form ; although the white 

 ones remain unchanged in appearance. After a further and careful examina- 

 tion of this " slightly quivering blood, we may at length see a minute thread- 

 like organism, with eel-like movements, emerge from the mass of corpuscles 

 and move slowly forward, or we may observe the little being tugging, with all 

 its might, at a red corpuscle, endeavouring to detach it from its rouleau " 

 {Steel). The parasite is about ^th of the diameter of a red corpiiscle in thick- 

 ness, and is from three to six times its length. It seems to have a thick body 

 and a spiral tail. 



MANNER AND TIINIE OF INVASION.— It appears from the investiga- 

 tions of Lingard, that this microbe, perhaps in another form, can live in water 

 outside of the animal body. In the Bombay Presidency it has been found in 

 the blood of a large proportion of rats and bandicoots, the health of which 

 rodents it affects but little. Stagnant water and grass growing on lately 

 inundated land, form favourable resting-places for the infusorian. Lingard 

 considers that it can be conveyed to horses in water and herbage, and in 

 grain containing the excrements of rats and bandicoots affected with the 

 disease ; but also thinks it is probable that flies act as carriers of surra from 

 infected horses to sound ones, which is a supposition that is strongly sup- 

 ported by the fact that nagana (p. 459) is transmitted by the tsetse fly. 

 This kind of fever seems incapable of being transmitted, under ordinary 

 circumstances, from one animal to another, except by inoculation. 



Although cases of surra may be met with all through the year, its microbes 

 are particularly active during the rainy season. When outside the animal 

 body and in a dry state, they are killed or rendered inert by prolonged 

 atmospheric heat. 



THE PERIOD OF INCUBATION seems to be liable to great 

 variations. It may be put at 6 or 8 days after inoculation or in- 

 gestion of blood taken from an animal suffering from surra. It 

 appears from Lingard's investigations that the period of latency 

 may be prolonged to 13 days, if the blood used for the inoculation 

 has been taken from the dead animal; and that when the para- 



