58 REPORT ON DOURINE. 



plasm odial form, after the latter had been deposited in tbe plaque, 

 but this is a point which will require further research work. In 

 Surra the course of the disease is marked by the absence of cutane- 

 ous plaques, and the eruption of a disseminated but localized 

 Urticaria is far less common than in Dourine. This may perhaps 

 indicate that the trypanosoma of Dourine elaborates a toxin of 

 greater vaso-motor toxicity than the trypanosoma of Surra. 



VI. What changes take place in the form of the trypanosoma 

 during the persistence of a plaque ? The microscopical changes 

 in the blood or serosanguinous fluid collected daily from the raised 

 cutaneous tumour have been examined in two typical forms of 

 Dourine plaques, viz. : 



(a) The cedematous plaque. 



(b) The flat disc-shaped plaque. 



(a) The cedematous. The plaque No. 2 about to be described 

 as occurring in mare VI 1 appeared on the morning- of the 18th 

 August 1903; it was circular in form, 1'5 inches diameter and 

 slightly depressed in the centre. On the 19th its diameter had 

 increased to 2 inches and on the third day the plaque became 

 somewhat oval 2' 5 by 2'0 inches, and of meniscus form. During 

 the two following days no change occurred, but between the 23rd 

 and 25th the plaque gradually decreased in size and it had dis- 

 appeared on the morning of the 26th. A full record of the number 

 and the different forms of the mature and developmental trypano- 

 somata fcund daily in stained specimens of blood drawn from 

 this plaque have been made. In the subjoined account it will 

 only be necessary to refer to the mature parasite and to its amoeboid 

 and plasmodial forms without entering into details with regard to 

 their distinctive features. On the first day the trypanosoma was 

 present, in small numbers, each individual protozoon having only 

 one macro and micro-nucleus. In addition, eight amoeboid forms were 

 found in two cover-glass specimens of blood. These numbers 

 gradually increased until the fourth day, when eighteen times 

 more trypanosomata were present, but only half the number of 

 developmental forms found on the first day were detected. On the 

 fifth day the numbers remained stationary, and were almost 

 identical with those noted during the previous twenty-four hours. 



