MYXOMATA. 175 



by their great firmness and density ; should the entire tumour 

 liave been converted into bone, the osteoid-chondroma is said to 

 have become an osteoma. 



As regards its innocence or mahgnity, we cannot venture to 

 pronounce any decided judgment, owing to the small number of 

 cases which have been hitherto recorded. The elements of pro- 

 gnosis laid down for enchondromata may be held (at least pro- 

 visionally) to be applicable to this variety likewise. 



d. Myxomata or Mucous Tumours. 



§ 141. A summary of all that has been said in the sections 

 treating of mucous tissue shows us that, although it is to be 

 regarded as a thoroughly independent and vitally active member 

 of the connective series, it nevertheless originates, in the vast 

 majority of cases, by a secondary metamorphosis of other con- 

 nective substances (§ 42) entering into the formation of tumours. 

 We have become acquainted with a myxomatous variety of sar- 

 coma, lipoma, and enchondroma respectively, understanding 

 thereby tumours, circumscribed patches of whose proper sub- 

 stance had undergone conversion into mucous tissue. It must 

 be admitted that this order of sequence is an inference from the 

 coexistence of these modifications ; but the possibility of a myxo- 

 matous metamorphosis of cartilage, adipose tissue, and areolar 

 connective tissue, has been established by observations so nume- 

 rous and well authenticated, that we are quite justified in assuming 

 the sequence to have been such as we have stated, and not of an 

 inverse order ; moreover, we have good grounds for preferring 

 such a conclusion (at least in the majority of instances) to the 

 hypothesis of a simultaneous development of compound types of 

 tissue. Bearing this well in mind, it seems at least prudent to 

 restrict the term '^ mucous tumour" to such growths only as are 

 exclusively made up of mucous tissue. Such tumours indeed 

 are not common ; they are common enough however to warrant 

 us in maintaining the group of tny.vomata as originally consti- 

 tuted by Virchow. 



§ 142. The definition of mucous tissue implies the existence 

 only of a basis-substance containing mucus, or of one which has 

 undergone mucous softening ; it involves no theory concerning 

 the form and character of the cells ; it allows us therefore to set 



