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The condition has been described as occurring mainly in 

 India, Africa, and tropical America. 



For the most part the descriptions both of the pathology 

 and the associated larvae have been neither very accurate 

 nor full. 



Railliet in his report deals extensively with the researches 

 of Descazeaux, who studied the condition in Brazil. Des- 

 cazeaux conducted some careful observations, and his contribu- 

 tion has considerably advanced our knowledge of the affection. 



The following is a brief summary of the description as 

 given by Descazeaux : — 



"Summer sores" .appear during the summer; during the 

 winter these tumours disappear totally or in part, to reappear on 

 the first return of heat. Three to 4 per cent, of horses and mules 

 were found affected. The parts of the body most affected are the 

 external surfaces of the extremities, the canon, the knee, and the 

 lateral and superior parts of the neck. The condition is found in 

 two stages. In the first stage the tumour is only inflammatory. 

 Old lesions will again become active. The tumours are circular, 

 non-adherent, and 1 to 1*5 cm. in thickness. In the second stage 

 (15 to 20 days) the circular tumour varies in extent up to 30 cm. 

 in diameter and 2 to 5 cm. in thickness ; it is very fibrous and 

 adherent to subjacent tissues, the superior part of the tumour 

 being ulcerated. The tumour presents a tendency to enlarge. 

 The surrounding skin is thickened, indurated, and elevated by a 

 number of nodules, which soon ulcerate and become confluent. 

 The ulcerated surface becomes covered by granulations. Pruritus 

 is intense. The sores last six to nine months, and resist all treat- 

 ment. Cold acts favourably upon them, and in the first months 

 of the winter, if they are not very extensive, they may completely 

 heal. If the sore is only in the first stage it will disappear in 

 from four to six days. 



Pathological Anatomy. — At first the "Esponja" has the 

 characteristics of an inflammatory tumour ; it is very vascular 

 and easily excised. Later the tumour becomes hard, fibrous, and 

 infiltrated with calcareous ••grains." On the cut surface these 

 ■'grains" are seen to vary in size from that of a pin's head to 

 that of a pea, and they enucleate very easily. 



Microscopical. — The tumour in the first stage shows roughly 

 three layers or areas — a deep layer formed by loose fibrous tissue 

 and vascular spaces ; a middle layer with little fibrous tissue but 

 a considerable infiltration of leucocytes and eosinophiles ; a 

 superior layer formed chiefly of thickened fibrous tissue. In the 

 middle, parasitic caseous areas are seen. These are oblong or 

 round, measuring from 800 /* to 900 ' /* in length by 

 300 /j. to 400 fi in breadth. 



The worms are found in these necrotic areas, and vary from 

 two to five in number. Some areas present a central cavity which 

 was primarily occupied by the parasite. In tumours of the second 

 stage it is difficult to find typical parasitic "tubercles. " The 

 tumours consist mainly of dense fibrous tissue. Sometimes the 

 debris of a parasite is seen. 



Descazeaux also gives a description of the "parasite" 

 which as Railliet has shown, he wrongly considered to be a 

 mature female. This parasite he calls the "constant parasite," 



