SUERA. 527 



inside the nostrils, as yellow scabs, for a day or two. Successive 

 crops of blood-spots appear on the membranes of the eyes, and 

 are characteristic of this disease; in that they are few, or even 

 absent, when the parasites are active in the blood ; and are well 

 marked and numerous during the decline of the fever. These 

 more or less purple blood-spots are due to the transudation of 

 blood from the blood-vessels " [Steel). The blood, if drawn, will 

 be found to be of an abnormally dark colour, which fact is due to 

 the destruction of red corpuscles, the office of which is to carry 

 oxygen for the purification of that fluid. In advanced cases, the 

 cornea may become opaque, with a tendency to ulcerate. A 

 yellow, semi-gelatinous exudation takes place in the loose tissue 

 under the skin. 



Steel noticed post-mortem in about two-thirds of his cases among 

 mules in Burma, ulceration of the stomach, which was not brought 

 on by the administration of drugs or irritating food, and which, 

 according to Lingard, is a result of surra. 



" The most common periods during treatment by arsenic in which 

 the haematozoon re-appears in the circulation of equines whose 

 systems are under the influence of the drug, is somewhere about 

 the 25th, 50th, or 75th day of an intermission, i.e., subsequent to 

 the disappearance of the organism from the circulation of the 

 animal. This gives one an idea of the deterrent effect produced 

 on the immature form, of the surra haematozoon, and its great 

 tenacity of life ; for in ordinary cases of the surra, the intermission 

 between the paroxysms, rarely if ever exceeds a maximum duration 

 of seven days " (Lingard). 



POST-MORTEM APPEARANCES.— As a rule, there is great 

 emaciation; enlargement of the liver and spleen; blood-spots 

 (petechiae) on various internal organs ; and a deposit of a yellow 

 or amber-coloured jelly or jelly-like fluid under the skin of the 

 throat, chest and abdomen, about the muscles and other tissues, 

 and especially round the base of the heart. The lungs often show 

 signs of inflammation. The mucous membranes and other tissues 

 are frequently tinged yellow, on account of the breaking up of red 

 corpuscles of the blood, by the surra parasites (p. 525). " I am of 

 opinion that in all cases of death from chronic surra, or in animals 

 which have been destroyed after the disea.se has been in existence 

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

 sive, will be seen post-mortem " (Lingard). 



NATUHE OP THE DISEASE.— Surra is due to the presence, in the 

 blood, of a microbe (Trypanosoma Evansi), which belongs to the animal 

 kingdom, and lives and breeds in that fluid. This parasite always exists 

 in uie blood of surra-afiected horses during the. frequently recurring feverish 



