^68 SURRA 



ever, are the occasional appearance of an urticarial erup- 

 tion, general or localized, closely following the first rise of 

 temperature, but which may make its appearance at any time 

 during the course of the disease ; then the presence of 

 petechiae on the mucous membranes, chiefly that covering the 

 membrana nictitans, lachrymation and the exudation of a 

 semi-gelatinous material into the subcutaneous and other con- 

 nective tissues. There is rapid wasting and great weakness, 

 although in the majority of cases the appetite remains good 

 throughout, no matter how high the fever. There is extreme 

 pallor of the visible mucous membranes, and this is followed at 

 a later period by yellowness. From first to last there is pro- 

 gressive anaemia ; the blood at first presents a normal char- 

 acter, but after a varying period of time it undergoes marked 

 changes. The white corpuscles are increased in number and 

 the red corpuscles usually cease to form normal rouleaux, lose 

 their individuality and run together forming irregular masses. 

 They are at first dark, but gradually, as the disease advances, 

 almost entirely lose their coloring matter and become pale.'' 



The respective duration of the paroxysms and intermissions 

 is very irregular. Lingaid puts it down as from one to six 

 days. He states that in a few experimental horses the 

 paroxysms lasted from eighteen to twenty-two days. 



The period of incubation seems to be liable to great varia- 

 tions. It may be put from six to eight days after inoculation 

 or ingestion of blood taken from an animal suffering from 

 surra. It appears from Lingard's investigation that the period, 

 of latency may be prolonged to thirteen days, if the blood used 

 for inoculation has been taken from' a dead animal. \\'hen the 

 parasites have been given in water, by the mouth, symptoms 

 of surra may not appear for even seventy-five days. We have 

 no exact data for determining the time required for the disease 

 to become manifest under natural conditions from drinking 

 surra contaminated water. Gunn states that the average dura- 

 tion of the disease is about fifty-two days. 



§ 20I. Morbid anatomy. As a rule there is great 

 •emaciation, enlargement of the liver and spleen, petechiae on 

 various internal organs, and a yellow^ or amber colored jelly- 



