526 GENERAL ANATOMY. 



These tissues may be divided into two kinds: 1st, tissues 

 analogous to those of the'healthy organization; 



2d. Heterologous tissues or tissues without analogy in the 

 regular organization. 



There are also some accidental tissues, intermediate, so to 

 speak, between the one and the o^her, analogous, if not with 

 any thing in the human organization, at least with that of 

 other animals. 



830. These different kinds of tissues are sometimes iso- 

 lated, at others, and frequently, united or combined with each 

 other. They are even often united with accidental humours, 

 with living animals, with altered humours or tissues, &c. 



831. Among anatomists and pathologists, some (Dupiiy- 

 tren, Cruveilhier, &c.) regard accidental tissues as the result 

 of transformations experienced by the natural tissues: they call 

 the analogous accidental tissues, transformations properly so 

 called, and heterologous tissues, degenerations; others (J. 

 Hunter, Abernethy, Laennec, &c.) regard them as new or 

 epigenetic productions. It is a question very difficult to re- 

 solve; however, the last opinion appears to us the most con- 

 formable to observation. ' 



832. True transformations are very rare, and take place 

 only between nearly similar tissues: thus the cartilages of the 

 larynx change into bone; the mucous membrane exposed to 

 the air changes into skin, as the skin drawn into the interior, 

 by a cicatrix, becomes mucous membrane, &c. It is thus that 

 we see, in trees, roots change into branches, and reciprocally 

 branches into roots. But most of the pretended transforma- 

 tions are only productions: thus a cicatrix is a membrane en- 

 tirely new, and not the result of the transformation of denuded 

 tissues; thus cancer of the neck of the uterus, is the result of a 

 substance of new formation infiltrated into its tissue, which 

 has separated, compressed it, and brought on atrophy, and not 

 the result of a degeneration of this tissue. 



