202 



MODERN HORSE MANAGEMENT 



[chap. 



that is not ia perfect health, and eventually 

 gets into the blood. Here it meets even more 

 formidable enemies, because it has to face a great 

 number of very large white blood corpuscles 

 many times bigger than the microbe itself. We 

 will suppose that when it reaches this stage it 

 has been multiplied to several thousand bacilli, 

 suflScient to attack the white blood corpuscles. 

 It happens that the system is in bad health, and 

 that its white blood corpuscles are few in 

 number and are not in a fit state to fight ; also 

 that there are very few antitoxins in the blood 

 and, generally speaking, through the ill-health 

 of the animal or person, these microbes win their 

 battle, i.e. typhoid fever is contracted. It is 

 interesting to know how these white corpuscles 

 are often beaten. They destroy germs by eating 

 them, but when germs are very plentiful they 

 often over-eat themselves to such an extent that, 

 as it were, they drop some of these germs, being 

 unable to hold them, and thus allow them to 

 continue their destructive existence. 



793. Other Means of Destroying Disease 

 Microbes.— Having considered the means Nature 

 adopts to resist disease-producing animal and 

 vegetable organisms, we will consider what other 

 means there are of fighting these microbes. It 

 has been found that they can be killed by various 

 means, such as intense cold, heat, fresh air, 

 sunlight, pure water, and various chemicals, and 

 also by starvation. Anything that will destroy 

 pathogenic germ life is known as a germicide, 

 antiseptic, or disinfectant. 



794. The manner in which antiseptic agents 

 destroy germs varies considerably ; for instance, 

 distilled water will destroy bacteria by causing 

 them to swell and burst ; a solution of common 

 salt in water, stronger than a normal saline 

 solution (which is -85 per cent.), will do the 

 opposite ; it will cause them to lose their water 

 (that is in the protoplasm), and thus cause them 

 to shrivel up. Sunlight causes most germs to 

 shrivel up, and oxygen destroys many of them. 

 Most antiseptic chemicals have a chemical action 

 with them which causes death. Microbes are 

 starved by being removed from their host ; for- 

 tunately most bacteria, when entirely removed 

 from their host, can only live a few hours, and, 

 if in fresh air or sunlight, perhaps only half an 

 hour. 



But it must be remembered that in this case 

 they must be removed from their host, because 

 a scarlet fever microbe can undoubtedly live for 

 many weeks on a piece of the skin of the patient, 

 and the tuberculosis bacillus can live for weeks 

 on the sputum of a patient. Hence the grave 

 danger of consumptives spitting anywhere except 

 into antiseptic cuspidors, etc. 



795. There are, however, two species of bac- 

 teria that do not die when removed from their 

 host : those of lockjaw (tetanus) and anthrax. 

 These are both bacilli. They have a little spore 



attached to one end that possesses the power of 

 making the rest of the bacillus virulent when- 

 ever it comes in contact with animal tissue (such 

 as an open wound). Thus a tetanus microbe 

 may lie in a dormant state for years and years, 

 and yet, on coming in contact with the open 

 wound caused when a horse falls and cuts its 

 knees, it becomes virulent and produces the toxin. 

 This production of poison is not instantaneous, 

 because, if the horse is taken home and the wound 

 thoroughly syringed out with an antiseptic, the 

 dangers of lockjaw are slight. It is a marvellous 

 thing that dust procured from the tombs of Egypt 

 which had not been opened for two thousand 

 years contained anthrax and tetanus bacilli 

 that produced, after suitable cultivation, these 

 diseases in animals. 



796. Certain pathogenic microbes, as stated 

 before, are found in various quantities almost 

 everywhere where there is animal life. Those of 

 typhoid, pneumonia, and diphtheria are the 

 commonest. But these harmful microbes are 

 only found in large quantities on, in, or near an 

 infected animal or person, i.e. on the articles 

 handled by the patient, or the excreta, in the 

 sputum, etc., and not on things that have not 

 come in contact with an infected person or 

 animal. Thus, if we want to collect some 

 tuberculosis germs, we do not collect air from a 

 room or the dust from the street, because our 

 chances of collecting any would be small ; but 

 we would go to the sputum of a patient. Again, 

 for diphtheria we collect it from the throat of a 

 diphtheria patient. Air in a room, if very foul, 

 will contain a great number of bacteria attached 

 to the particles of dust, and so dust on a street 

 pavement will contain consumptive germs if con- 

 sumptives have been spitting into the street. 

 But under strict hygienic conditions the number 

 of pathogenic bacteria in the atmosphere would 

 do us no harm. The percentage of harmful 

 bacteria in the air varies very considerably. The 

 percentage of all kinds of bacteria also varies ; 

 this depends to a great extent on the number of 

 particles of dust in the air. Thus there are more 

 ijacteria in the city air than the country, and 

 very few in mountain air, whilst the air in 

 mid-ocean and on high mountains is free from 

 germs. 



797. There are thousands of bacteria in every 

 grain of soil ; uncultivated sandy soil contains 

 over 60,000 bacteria per grain, whilst highly 

 manured soils may contain 100,000, and sewage- 

 contaminated soils as many as 7,000,000 per 

 grain. The majority of these bacteria are non- 

 pathogenic, and without them agricultural cul- 

 tivation could not exist. Water, again, may 

 contain several thousand bacteria per cubic 

 centimetre. Pure spring water, after standing 

 in a flask at a certain temperature, may contain 

 several thousand bacteria per cubic centimetre, 

 but may be absolutely harmless to drink. The 



