512 GENEEAL DISEASES. 



development of the micro-organisms of tetanus. Suppurating wounds are 

 therefore particularly good breeding grounds for the bacilli of this disease. 

 Injury and the presence of foreign bodies also act favourably in the same 

 direction. Hence, we find that wounds which become polluted with soil 

 and dirt are specially liable to be followed by symptoms of this disease ; 

 and the lesson is obvious that the cleaner we keep wounds, the less danger 

 will there be of tetanus. 



It appears that the skin and mucous membrane, when unbroken and in a 

 healthy state, will bar the entrance, into the system, of the tetanus poison, 

 which, however, is capable of getting through the smallest breach existing 

 in these coverings. Before the nature of the disease was known, cases in 

 which a wound was evidently the point of infection were classed as those of 

 " traumatic tetanus ; " and cases in which no wound was discernible, as 

 those of " idiopathic tetanus." Such a, distinction is, with our present state 

 of knowledge, not alone unnecessary, but is misleading. As these bacilli 

 cannot develop in air (or rather in oxygen), punctured wounds are more 

 favourable to the production of tetanus than superficial ones. Also, as 

 there is a fair amount of oxygen in the blood, these microbes cannot live 

 in it, unless when it has lost a large proportion of its oxygen, and conse- 

 quently they remain, as a rule, in more or less close proximity to their 

 original point of entrance. The fact that the microbes of this disease very 

 rarely indeed obtain entrance from accidentally-inflicted clean-cut wounds, 

 is probably owing to the comparative freedom from contamination enjoyed 

 by these mjuries. No such immunity is possessed by clean-cut wounds 

 made by surgical instruments which have been employed in tetanus cases, 

 and which have not been thoroughly disinfected. These germs are 

 frequently found in some districts, and rarely in others. They appear to 

 be much more common in the tropics than in temperate climates. Nicolaier 

 proved that the subcutaneous moculation of earth often gave rise to 

 tetanus. In such cases it is almost needless to say that the inoculated earth 

 contained the spores of this disease and other micro-organisms which are 

 favourable to their developnient. We should, therefore, be particularly 

 careful to clean and thoroughly disinfect all wounds — such as broken knees, 

 overreaches, and ' especially punctured sole and frog — which are liable to 

 contamination from the soil. 



Bonome and other observers have proved that the microbes of tetanus, 

 when in the form of spores, can preserve their vitality even in boiling 

 water. The poison of tetanus can be destroyed by strong acids, like 

 carbolic acid or hydrochloric acid, by boiling water, or by keeping it for 

 five minutes at a temperature of 130° F. Hence, it does not appear 

 dangerous to allow animals (hounds, for instance) to consume the cooked 

 flesh of horses which have died of tetanus. Dogs are much less susceptible 

 to it than are horses. Hewlett states that direct sunlight destroys it in 

 from fifteen to eighteen hours' exposure ; and that it maintains its virulence 

 almost indefinitely in a cool dark place. These considerations and the fact 

 that tetanus germs cannot develop in air, teach us the advisability, in the 

 prevention of this and other diseases, of exposing, as much as practicable, 

 the bedding of our horses, and the interior of our stables, to the purifying 

 action of sunlight and fresh air. 



Tetanus, as we have seen, can occur only by inoculation. For all practical 

 purposes, we may accept as a fact that one horse cannot give it to another ; 

 although it might very easily be conveyed by an intermediate carrier, such 

 as the hands or instruments of a person who had been attending a case of 

 tetanus. It is. probable that when the disease follows a surgical operation, 

 the poison has been derived, as a rule, from infected instruments. The 

 wounds which are most generally followed by lockjaw, are those of castra- 

 tion, docking, broken knees, deep wounds in a limb, and especially punctures 

 in a foot. Wounds in the intestines (for instance, by worms) are probably 

 the usual points of entrance of these microbes, when the disease is conveyed 

 by means of food or water. 



