92 PRINCIPLES OF VETERINARY SURGERY 



The vagina, the uterus, the teat ducts, the conjunctiva, and 

 the external ear contain them. 



Bacteria, however, are not found in the living, healthy 

 tissues and humors of the body. The tissues other than the 

 skin and mucous membranes are free from micro-organisms 

 except in disease. The blood, the synovia, the serum of the 

 great cavities, and the cerebro-spinal fluid do not contain 

 micro-organisms in health, and even in mycotic diseases these 

 liquids, including the blood, do not often abound with them. 

 During the progress of disease the micro-organisms entering 

 the blood stream are promptly disposed of by the resisting 

 forces and emnmctories of the body. It is only as death 

 approaches, when the resisting forces are depressed and 

 exhausted, that microbian flora flourish within the body. 

 After death when the resistance is entirely removed, all the 

 tissues abound with them. 



Air itself is free from micro-organisms, but it is kept 

 more or less constantly contaminated by the dust and flying 

 particles it is capable of containing at all times in closely 

 inhabited districts, in buildings, streets, etc. The air of the 

 distant prairies, of the pine forest, the mountain, and in 

 sparsely inhabited regions in general is comparatively free 

 from pathogenic microbian agents. "Wherever man, ani- 

 mals or even plants live, die and decompose, bacteria are 

 .sure to be present" (McFarland). Decomposing organic 

 matter, cesspools, manure-heaps, dead animal-bodies, seethe 

 with them. The upper layers of well-tilled soil abound with 

 all kinds of microbian flora, but the lower layers are relatively 

 free from them owing to the absence of the nitrogenous 

 ■ food necessary for their support. Water of the city hydrant, 

 the dug well, rivers, creeks, ponds, lakes, etc., is seldom 

 ever free from bacteria. They are, however, not found in the 

 water of deep, drilled wells and springs that are not contami- 

 nated from the surface. 



