4i8 



Tumors. 



gland tissue (adenocystoma). These entodermal cysts are lined 

 by columnar epithelium, sometimes ciliated, and in man are found 

 in the liver, intestine or peritoneum, in the neighborhood of the 

 trachea and bronchi, and in the neck, var\ing- in size from that 

 of a pin-head to that of an adult human head. In animals they 

 most usually arise from rests of the original urinary structures, 



Fig. 127. 

 Cystic kidney of hog (section). 



the Miillerian or AVolffian ducts, and are found as transparent 

 vesicles of the size of a millet seed or pea or sometimes larger, 

 along the broad ligaments of the uterus, in the fimbriae of the 

 oviduct, and in the epididymis. The congenital cysts of the 

 ovary, occurring as single or multilocular and closely packed 

 cysts of this organ, and containing a thin mucoid and sometimes 

 bloody material, are further examples of the same type. Con- 

 genital cysts of the kidney are also regarded as results of devel- 

 opmental disturbances, converting the kidneys, usually bilater- 

 ally, into a grape-like mass of vesicles with watery contents, 

 between which an inconspicuous amount of parenchyma is found 

 reduced mainly to thin connective tissue septa (cystic kidneys, 

 vesiculated kidneys). This anomaly is supposed to be due to a 

 failure of union between the uriniferous tubules and the develop- 

 ing glomeruli, these two parts growing separately (Ribbert). 

 The term odontoma and odontohlastoma are applied to mon- 



