1G2 



ON THE PROCESSES OF 



want the space which the dead part occupies, and the aid which it for- 

 merly contributed. .It is obvious that two processes are here necessary : 

 the dead part must be carried off, and its post must be filled up by a sub- 

 stitute of new matter possessing the precise properties of the old. And 

 here we meet with a clear and striking instance of that wonderful in- 

 stinctive power which pervades every portion of the vital systems, both of 

 the animal and vegetable world, and which is perpetually prompting them 

 to a repair of whatever evils they may encounter, by the most skilful and 

 definite methods. 



In order to comply with this double demand of carrying off the dead 

 matter, and of providing a substitute of new, each of the systems before 

 us commences, in the living substance that immediately surrounds that 

 which requires removal, a new mode and a new degree of action. A 

 boundary line is first instinctively drawn between the dead and useless, 

 and the living and active parts ; and the latter retract and separate them- 

 selves from the former, as though the two had been skilfully divided by a 

 knife. This process being completed, the mouths of the surrounding ab- 

 sorbent vessels set to work with new and increased power, and drink up 

 and carry off whatever the material may be of which the dead part con- 

 sists, whether fat, muscle, ligament, cartilage, or bone ; the whole is 

 equally imbibed and taken away, and the hollow is produced, where the 

 dead part existed. At the same time the mouths of the corresponding 

 secernent vessels commence a similar increase and newness of action, 

 and instead of the usual lymph, pour forth into the hollow a soft, bland, 

 creamy, and inodorous fluid which is denominated pus ; that progressively 

 fills up the cavity, presses gradually against the superincumbent skin, in 

 the gentlest manner possible distends and attenuates it, and at length 

 bursts it open, and exposes the whole of the interior to the action of the 

 gases of the atmosphere. 



It was at one time conceived, and by writers of considerable eminence 

 and judgment, and of as late a date as the time of Mr. Hewson, that the 

 injured and dead parts were themselves dissolved and converted into pus ; I 

 but this opinion has been disproved in the most satisfactory manner by 

 the minute and accurate experiments of Mr. John Hunter, Sir Everard 

 Home, and Mr. Cruickshank ; and the process has been completely 

 established as I have now related it. 



In what immediate way the gases of the atmosphere operate so as to 

 assist the secernent mouths of what is now the clean and exposed surface 

 of a wound, in producing incarnation, or the formation of new matter of 

 the very samfe kind and power as that which has been carried off, and ena- 

 ble them to fill up the cavity with such new matter, and perfect the cure, 

 we do not exactly know. Various theories have been offered upon this 

 very curious subject ; but at present they are theories, and nothing more ; 

 and I shall not, therefore, detain you with a relation of them. Thus 

 much, however, we do know, that the co-operation of the atmosphere 

 with the action of the mouths of the secernent system engaged in the 

 work of restoration is, in some way or other, peculiarly beneficial ; and 

 that, generally speaking, the wider the opening, and the freer the access 

 of atmospheric air of a due temperature to the surface of the wound, or, 

 which is the same thing, the freer it comes in contact with the mouths of 

 the secernent vessels, the more rapidly and auspiciously the work of im- 

 pletion and assimilation proceeds. Neither do we know, precisely, why 

 pus. rather than any other kind of fluid, should in the first instance be 



