BACTEEIA. 63 



METHODS OF REPAIR.— For practical purposes, we may adopt Eaget's 

 classification, which is as follows : ^1.) Immediate union. Here, the parts 

 being brought into exact cogtact, unite in a few hours, without any per- 

 ceptible material being deposited between them ; hence there is no visible 

 scar. To obtain this result, which would be rarely possible in horses, the 

 inflammation must have \>een very slight. (2.) Union by primary adhesion. 

 Ill this, the divided surfaces are glazed over by a fluid which is exuded from 

 them, or by the coagulation of a thin film of blood, either one, or both, of 

 which substances may form in two or three days a temporary means of 

 union, which material, as explained by Hamilton, will have to be absorbed 

 before permanent union, which will leave a scar, can take place. In fact, 

 the greater the quantity of this temporary adhesive material, the longer 

 will the wound take to heal. (3.) Granulation. This is a tedious process 

 which is invariably accompanied by the formation of pus, and is the one by 

 which, as a rule, all wounds, except clean-cut ones, heal. (4.) Union of 

 granulating surfaces. (5.) Healing under a scab. All wounds h^al in 

 essentially the same manner, namely, by the growth and organisation of 

 new tissue from corresponding old tissues already present in the part. 

 The whole process is, strictly speaking, one of growth followed by organisa- 

 tion, and any differences which wounds present in bringing this 'to a 

 successful issue are mefely superficial. 



BACTERIA AND DISEASE GERMS.— Soil, water, and to a less extent 

 air are filled with microscopic germs (bacteria) whose function is to set up 

 decomposition in animal and vegetable matter that is in a fit condition for 

 this change. Some of these germs (those of pus) cause putrefaction ; and 

 others, respectively, give rise to special diseases, such as tetanus, and 

 various kinds of fever. Putrefactive germs are always present. The 

 microbes of special diseases are only occasional visitors, or their numbers 

 are usually too few to injuriously affect the system. In health, the skin 

 and mucous membrane protect the body more or less eflSciently from the 

 action of bacteria. When either of these coverings become injured, as in 

 the case of a wound or bruise, the underlying tissues are rendered specially 

 liable to an attack of these germs, which fact is shown by the tendency that 

 the seat of hiirt has, in these cases, to form "matter" (pus); in other 

 words, to suppurate. I have already explained that ordinary pus, like 

 gastric juice, has the power of dissolving the tissues. Hence its unchecked 

 presence in a part is characterised by the formation of matter resulting 

 from tissue destruction. This diseased product (pus) may appear as a 

 discharge from a wound, or as a collection of fluid in an abscess. The skin 

 which covers an abscess becomes thin and weak, owing to the corroding 

 action of the contained pus (p. IS) ■ the usual result being that the abscess, 

 if circumscribed in a sac, will in time tend to " point." 



Contrary to what we might suppose, living tissues ajid blood do not 

 form a particularly suitable place of residence for putrefactive and disease 

 germs, especially if these microbes, as in ordinary air, are comparatively 

 few in number. Also, the tissues have the power of resisting, to a certain- 

 extent, their inroad, and even of destroying them. Thus, the liability of a 

 wound to infection, is influenced by the number of the germs, and by the 

 resistance (or health) of the part. From these considerations and from 

 experience we see that clean cut wounds which are exposed only to ordinary 

 fresh air, will continue healthy for a far longer time than those which have 

 become tainted with dirt and especially with decomposing matter, in which 

 bacteria teem. Impure air, particularly, when loaded with dust, has highly 

 infective properties; and water which is fit for drinking has only feeblv 

 infective power. A most important point to remember is, that moisture 

 favours the development and multiplication of bacteria ; hence lie drier a 

 wound is kept, the better will it resist their attack. I may add as an 

 illustration bearing oa this subject, that the more concentrated meat soup 



