422 SIMPLE TUMOURS. 



X.— PArvASITIC CYSTS. 



The compound cysts include the hydatid larval conditions of 

 many parasites, such as — 



Cysticercus hovis — in the muscles of horned cattle. 

 „ cellnlosce — muscles of the pig. 



„ pisiformis — entrails of hares, &c. 



„ cucumcrinus — body of dog louse. 



„ tcnuicollis — liver, walls of mesentery, pleura, 



pericardium, diaphragm, &c. of sheep and 

 pigs. _ 

 „ fasciolaris — liver of rat and mouse. 



Eccliinococcus vcterinorum — large bladder-worms in liver, 



heart, lungs, &c. 

 Canurus cerebralis — in brain of herbivora, particularly sheep. 



Of these, however, the Coenurus cerebralis and the Ucchincocci 

 are the only ones which attain any size. 



XI. — CYSTIC TUMOURS OR CYSTS 



Are not now regarded as tumours in the strict sense of the 

 term. They are cavities containing a liquid or pultaceous 

 matter, enclosed in a more or less distinct capsule, which may 

 be a new formation or a pre-existing structure, distinctly 

 extravasated with or by its own secretion. Paget divided them 

 into simple or barren, and compound or proliferous. 



The barren cysts contain a fluid-like serum, such as that 

 found in serous abscesses (capped elbow and capped hock), or 

 synovia-like fluid, as in the enlarged bursas (wind-galls) ; whilst 

 others contain a more highly organised fluid, as in ranula. 



These cysts, according to the same authority, have at least 

 three modes of origin. 1st. Some are formed by the enlarge- 

 ment and fusion of the spaces or areolae of the connective or 

 other tissues. In these spaces fluids accumulate ; the tissues 

 become rarefied, and gradually the boundaries of the spaces are 

 levelled down and walled in, till a perfect sac or cyst is formed, 

 the walls of which continue to secrete. 



2d. Some cysts are formed by dilatation and growth of natural 

 ducts or sacculi, as are those sebaceous or epidermal cysts, 

 which, formed by hair follicles, have permanent openings. Such 



