PRINCIPLES OF VETERINARY SURGERY 537 



foci of recent formation, and deserves the name of melan- 

 otic nodule. The nodules, enclosed in the cellular tissue, are 

 of globular aspect, and divided into round secondary lobes 

 of fibrous septa harboring black foci of the disease. The 

 blood vessels are but few and slightly developed, and the 

 cells of which the tumor is composed all belong to the con- 

 nective types. These cells are found in every stage of de- 

 velopment, from the young cell to the fibrillary adult tissue. 

 The small round embryonic cell of true sarcoma is nevej 

 encountered. These nodules are constituted by the reaction 

 of the tissues and the more or less abundant proliferation 

 of the connective tissue cells, but the process is rather more 

 exuberant than destructive. It simulates the fibrous tubercle 

 more than the sarcoma or fibroma. The elongated and spindle 

 form of the elements of the nodule has caused the majority of 

 writers to confound them with sarcomata or fibromata, so 

 that they are almost always described under the name of 

 melanotic-fasciculated sarcomata. 



The three forms are seldom pure and isolated. Even in 

 the same tumor a cyst may be found associated with the 

 nodules. The organs in which melanism may be observed 

 are: 



I. Connective Tissue. Every portion of the connective 

 tissue may be invaded. The connective tissue constituting 

 the cutaneous derma (true skin) usually presents the first 

 perceptible alterations, but since the epithelial covering has 

 a share in the process it deserves separate consideration. 

 The subcutaneous intraglandular and intramuscular connec- 

 tive tissues exhibit every variety of melanosis, but it seems 

 that they are invaded later than the skin. The loose connec- 

 tive tissue at the entrance of the thoracic and pelvic cavities 

 is frequently invaded. Tumors of considerable size have 

 been found around the bladder and the rectum. In the pelvic 

 cavity the masses may suri'ound the kidneys, the ureters, the 



