DEGENERATION. 357 



composed of processes, which belong, some of them, 

 rather to the active class, and some of them, rather to 

 the passive one ; and the obvious results are in many 

 cases apparently so similar in both classes, that the ulti- 

 mate changes which we meet with, after the continuance 

 of the process for a certain time, may very nearly be 

 the same. Here particularly it was for a time, very 

 difficult to define the boundaries, and a great part' 

 of the confusion which marked early microscopical 

 efforts, was occasioned by the extraordinary difficulty 

 there was in separating active and passive disturbances. 



Passive disturbances I call those changes in cellular 

 elements, whereby they at once either merely lose a por- 

 tion of their activity, or are so completely destroyed, that 

 a loss of substance, a diminution in the sum total of the 

 constituents of the body is produced. Both series of pas- 

 sive processes, taken together, viz., those which are in the 

 first instance marked by an essential diminution of power, 

 and those which terminate in a complete destruction of 

 the parts, constitute the chief part of the domain of what 

 is called degeneration, although a point that we must 

 hereafter consider more closely a great part of what 

 must be called degeneration must be transferred to the 

 series of active processes. 



It makes of course an extremely great difference whe- 

 ther a vital element continues to subsist as such, or whe- 

 ther it entirely and completely perishes : whether at the 

 conclusion of the process, it still exists, even though in a 

 condition of much diminished functional power, or whe- 

 ther it is altogether destroyed. And here we have the 

 important practical distinction, that in the one series of 

 processes there is a possibility of a repair of the cells, 

 whilst in the other direct repair is impossible, and a rege- 

 neration can only take place by means of a substitution 

 of new cells from the neighbourhood. For when a coll 



