COMPOUND NATURE OF TUMORS. 501 



ning to attain their full development. In the case of 

 many new-formations, retrograde metamorphosis begins 

 comparatively so early, nay constitutes to such a degree 

 what is ordinarily met with, that the best investigators 

 have looked upon its different stages as the really 

 characteristic ones. In the case of tubercle, for exam- 

 ple, we find that the majority of all modern observers 

 who have made it their professed study, have taken its 

 stage of retrograde metamorphosis for the real typical 

 one, and that inferences have hence been drawn with 

 regard to the nature of the whole process, which with 

 equal right might have been drawn with regard to the 

 different stages of the retrograde metamorphosis of pus 

 and cancer. 



We are as yet able in the case of very few elements 

 to give in numbers with absolute certainty the average 

 length of their life. There manifestly exist variations 

 similar to those we meet with in normal organs. But 

 among all pathological new-formations with fluid inter- 

 cellular substance there is not a single one, which is 

 able to preserve its existence for any length of time, 

 not a single one, whose elements can become permanent 

 constituents of the body, or exist as long as the indi- 

 vidual. This may no doubt seem doubtful, because 

 many forms of malignant tumours subsist for many 

 years, and the individual retains them from the time of 

 their development until his death, which may perhaps 

 occur at a very advanced age. But the tumour as a 

 whole must be distinguished from its individual parts. In 

 a cancerous tumour which lasts for many years, the 

 same elements do not last the whole time, but within 

 its limits there occurs a frequently very numerous suc- 

 cession of fresh formations. The first development of a 

 tumour takes place at a definite point,' but its subse- 

 quent growth does not consist in the production of a 



