TUMOMS. 479 



12. Carcinoma. 



This simple division and nomenclature, as a matter of course, 

 admits of many subdivisions and combinations. All secondary 

 changes, however, must be separated from the primary forms of 

 tumors, as enumerated in the above system. 



1. MYXOMA. MUCOID TUMOR. 



Myxoma or mucoid tumor is a soft, jelly-like, half -transpar- 

 ent growth, either sessile or pedunculated, composed of myxoma- 

 tous connective tissue. Blood-vessels are sometimes abundant, 

 at other times the supply is scanty. Myxoma may combine with 

 other varieties of connective tissue ; frequently, also, it accom- 

 panies glandular new formation. 



According to the different varieties of myxomatous tissue 

 (see page 147), myxoma appears in the following forms : 



(a) Myxoma of Reticular Structure. This is composed of a deli- 

 cate fibrous reticulum, holding chiefly at its points of intersection 

 nucleus-like oblong plastids. In the meshes of the net-work there 

 is a gelatinous, apparently homogeneous, basis-substance, which, 

 upon being stained with chloride of gold, exhibits a delicate 

 bioplassou reticulum. In the centers of the spaces lie single, 

 double, or multiple plastids, some of which are about the size of 

 a nucleus, while others show a finely granular zone of bioplasson 

 around the nucleus. All plastids are connected by means of 

 delicate filaments with the bioplasson contained in the basis- 

 substance. (See Fig. 181.) 



This variety of myxoma is sometimes scantily, sometimes 

 freely, supplied with blood-vessels. In the latter case the vessels, 

 though they have the character of capillaries, are very broad and 

 lined with large endothelia, and in their neighborhood the reticu- 

 lum is always narrower and richer in plastids than is the rest of 

 the tissue. It is this variety which is often combined with gland- 

 ular new formations of both the acinous and tubular varieties, 

 and then produces, if pediculated, the so-called polypoid tumors 

 of the mucous membranes. (See article " Adenoma.") Plastids 

 crowding the meshes of the reticulum are found either in rapidly 

 growing or in recurrerit tumors, which are gradually assuming 

 the malignant type of myxo-myeloma. 



Myxomata of reticular structure are observed in the skin as 

 flat, sessile, or pediculated, smooth or raspberry-like tumors, or 

 they may be corrugated or lobate, and are often highly vascular- 



