82 CYSTS. 



known course of development in dendritic outgrowths.. A 

 simple papilLa is in every case the starting-point of the whole 

 series of changes ; at some point of its surface it gives off a 

 lateral sprout, a fresh papilla ; we thus get a forked process, or 

 a trunk with two branches. The phenomenon repeats itself, and 

 underlies the most complex ramifications of the morbid growth. 



In bringing this general view of the subject to a conclusion, 

 I would remark that the morphological nomenclature given above 

 is very lax — that the terms pass into one another by imper- 

 ceptible gradations ; and I insist on this fact mainly because it 

 gives me another opportunity of combating the pre-histological 

 delusion that, when w^e have described the naked-eye appear- 

 ances of a new growth, we have got any nearer to its essential 

 characters. This mistaken notion was excusable enough so long 

 as minute investigation had to contend with greater difficulties 

 than those wdiich now beset its path ; it was excusable, moreover, 

 because certain morbid growths adopt one form in preference to 

 others ; nay, some of them occur only as fungi, as polypi, as 

 papilla?, &c. But this, of course, does not preclude other pro- 

 ducts of morbid growth from assuming the same forms. And 

 what is true of external form is equally true of the remaining 

 naked-eye characters — of size, consistency, and colour — all of 

 which have been employed as principles of classification in the 

 same mistaken way. * 



§ 70. By way of appendix, I will here allude to a peculiar 

 element of structure which may complicate the most various 

 forms of morbid growth — I mean the cyst. This term includes 

 every sharply circumscribed globular or spheroidal cavity filled 

 with fluid. This definition does not take the cyst-w^all into 

 account ; for although a special cyst-wall, or sac (Balg) is 

 often present, yet it is not invariably so. The contents of 

 different cysts dififer widely from one another. They may be 

 thin, and clear as water ; they may be greasy or pasty ; nay, 

 they may even be so thick as hardly to allow of their being 

 called fluid at all. These varieties essentially depend upon the 

 mode in which the cysts originate. And here we have to dis- 

 criminate between — 



* Particularly as regardvS tumours. Cf. Vircliov:, " Die Lehre von den 

 Krankhaften GeschTriilsten." Berlin. 1864. 



