364 Surgical Diseases and Surgery of the Dog 



(4) Cysts — Abnormal encapsulated collections of fluid. 



(b) Compound Tumors — Tumors formed of several 

 tissues. 



(1) Hypertrophy and Hyperplasia 



(a) Hypertrophy is commonly seen in organs which have 

 sustained an increase in functional activity. Thus, we see a 

 simple "accommodative" hypertrophy of the Uterus during preg- 

 nancy with increase of size in the individual cells. The Cervix 

 Uteri is also occasionally the seat of hypertrophy. Hypertrophy 

 of the muscularis of the Bladder is sometimes seen when that 

 organ contains calculi of large size. Johne saw an increase two 

 or three times above normal. A similar condition is seen in the 

 wall of the Intestine on the proximal side of a constriction or 

 chronic obstruction. When one of bilateral organs takes on the 

 function of its fellow, it enlarges, and the condition is spoken of 

 as "compensatory" hypertrophy. Thus, when one Kidney becomes 

 hydronephrotic or is extirpated, or the renal artery is ligated, the 

 opposite kidney enlarges, Gibson found the Mesenteric Glands 

 distinctly enlarged in an animal that had undergone splenectomy 

 six months previously. Hypertrophy of the Muscularis of the 

 Heart is seen in varying degrees according to age, breed, sex, etc., 

 in certain diseases, and particularly the character of the ex- 

 ercise indulged in. Strictly speaking, that which is termed hyper- 

 trophy of the Heart is both hypertrophy and hyperplasia. The 

 hearts of hunting dogs are always relatively large. In old dogs a 

 general increase in the amount of all the component tissues leads to 

 hypertrophy of the Prostate Gland. The immediate cause of these 

 cases of enlarged prostate- is not known. Some have suggested 

 increased vascular supply, but this is inadequate. Leisering de- 

 scribed hypertrophy of the Sebaceous Glands situated on the pos- 

 terior aspect of the fore-leg. According to Kitt, the Intestinal 

 Villi may become hypertrophied to a size four times above normal 

 through the irritation produced by the burrowing of tape-worms. 



(b) Hypeorplasia. As will be mentioned under Fibromata, 

 no sharp distinction can be made between this condition and 

 fibrosis. Irritation will lead to proliferation of connective tissue. 

 A familiar example is seen in the Skin at points exposed to friction or 

 pressure. Enlargements of the Thyroid Gland depending upon in- 



