372 Surgical Diseases and Surgery of the Dog 



age cells do not develop from pre-existing cartilage cells, 

 but from what may be termed "mother cells" of cartilage. At 

 the edge of a growing chondroma there are cells of an embryonic 

 type, looking like ordinary connective tissue cells, and it is these 

 cells which proliferate, and their "daughter cells" develop a matrix 

 around them and become cartilage cells. So that such a chondroma 

 grows by the continuous accretion of new tissue at the peri- 

 phery. The cartilage cell as such is so surrounded by the matrix, 

 that manifestly it cannot form metastases, but these proliferative or 

 "mother cells" can easily be carried by the blood stream to the 

 various parts of the body, and coming to rest in suitable relation- 

 ships will then proliferate and the resulting cells become true car- 

 tilage cells. It is in these primary cartilaginous tumors that there 

 occurs later on the osteoid or truly osseous change. 



Mixed chondromata have been found in the Lungs (Cadeac), 

 the Thyroid ( Siedamgrotzky, Kitt), the Tympanic Cavity (Siedam- 

 grotzky), the Cardiac Valves (Hamburger), in the Nasal Cavity 

 (Kitt), on the Digits, and they are very common in the Mammary 

 Gland. Of two hundred and fifty-six tumors of the mammae re- 

 moved at the Alfort School between October 1871 and December 

 1876, two hundred and eleven were osteo-chondromata. 



Osteomata. These, the bony tumors, are not very common. 

 They are occasionally found on the Inferior Maxilla, the Penial 

 Bone, and on the Internal Face of the Cranium, particularly in dogs 

 suffering from ossifying pachymeningitis (Siedamgrotzky, Cadeac). 

 They have also been seen attached to the transverse process of a 

 Cervical Vertebra (Mueller), the Connective Tissue of the Neck 

 (Leisering), and on the Pulmonary Pleura (Vulpian). 



Lipomata. Pure fat ttunors are rare compared to other tu- 

 mors. They" are more liable to show other forms of connective 

 tissue, such as fibro-lipoma, lipo-myxoma. They occur most com- 

 monly as fibro-lipoma, and often attain enormous dimensions. They 

 are characterized by their subcutaneous situation, soft, lardaceous 

 texture, sharp demarcation, slow growth, and slight vascularity. 

 They are generally lobulated, due to septa of connective tissue. 

 In size, they may vary from a small nut to the human head. They 

 are the largest of all tumors. They are sometimes pendulous, and 

 not always round, but large and cylindrical. Froehner saw one 

 ten inches in length. Huidekoper saw one growing from the in- 



