288 Veterinary Medicine. 



Histogenesis. The source of these cysts has been much debated. 

 Many liave held with Spencer Wells that they have their origin 

 in dilated Graafian vesicles, and the discovery of an ovum in 

 the contents, b}^ Rokitansky and Ritchie showed at least that 

 this follicle had formed part of the cyst. On the other hand 

 Foster, Rivolta, Klebs, Malassez and others, constantly failed 

 to find ova or other distinct elements of the Graafian follicles, 

 but did find epithelial elements, and note that the cysts are at 

 an early stage connected with the surface of the ovary like the 

 ^^% tubes. These embryonic tubules of Pflueger are therefore 

 held to be the starting point for the cysts, which because of their 

 mixed epithelial as well as liquid contents, seem allied to adenoma. 

 From observations on the ovarian cysts of the lower animals 

 Galtier, attaches great importance to vascular obstructions. Ob- 

 struction by pressure or otherwise led to haemorrhages and 

 transudation of blood, and the cavities formed in this way be- 

 came the seats of epithelial growth, and liquid effusion. The 

 blood remained for a time as distinct clots, and was later indi- 

 cated by the pigmentation of the walls of the cyst. 



Lesions. The enlarged ovar}' may be uniformly rounded and 

 smooth, or it may be marked b}^ irregular bosses, giving it a 

 lobulated appearance. It is very va.scular, and is often covered 

 by a thickening of peritoneum. When multiple they are usually 

 closeh' adherent and may even be included one within another. 

 The individual cysts may be of the most varied sizes. The cystic 

 ovar\' has at times reached enormous dimensions : in the mare 46 

 lbs. (Bouley, Rivolta, Thiernesse): in the cow 250 lbs. (Rey- 

 nolds, Meyer): in the ewe 7 lbs. (Willis): in the sow 7 lbs. 

 (Reyer): in the bitch 15 lbs. (Bovett). The walls of the cj^st are 

 formed of connective tissue more or le.ss perfectl}^ organized, ar- 

 ranged it may be in several superposed layers (Galtier) and lined 

 or not by epithelial cells (cylindroid, nucleated, or of various 

 forms). They may be reddened by haemorrhages or pigmented 

 from former blood extravasations. The liquid contents may be 

 clear and water}^ white, straw yellow, or of a deeper 5'ellow, 

 brown or red. Among other constituents there are alkaline 

 chlorides and sulphates, albumen in solution or flakes, mucin, 

 fibrine, fattj^ granules and cholesterinecr3'Stals. In some instances 

 the}' contain pus cells (chronic abscess). 



