II Jan., 1909.] Diseases of Farm Animals 47 



Mechanical Antidotes include such substances as charcoal, earth, white 

 of eggs, flour gruel, starch gruel, milk, butter, oils and fats. These 

 either mechanically absorb or envelop the particles of poison and so retard 

 their absorption, or they ensheath and protect the mucous surfaces from 

 contact with the poison and so prevent irritation. Iheir use is principally 

 indicated in cases of irritant poisoning. The artificial production of 

 vomition and the emptying of the stomach with the stomach pump may be 

 regarded as mechanically antidotal measures. 



Chemical Antidotes are those which bv acting chemicallv on the 

 poison so change its character as to render it innocuous, whether b\ a lessen- 

 ing of causticity or by transforming it into an insoluble substance. For 

 instance, alkalies counteract acids, as when lime water is prescribed in 

 sulphuric acid poisoning the insoluble sulphate of lime is formed ; albumen 

 (in the form of white of egg) combines chemically with corrosive sublimate 

 and forms the insoluble and non-irritating albuminate of mercury ; and 

 sulphuric acid in contact with lead salts forms insoluble sulphate of lead. 



Physiological Antidotes, while having no action on the poison itself, 

 produce an effect on the animal directlv antagonistic tO' that produced 

 by the poison. Thus, stimulants are physiological antidotes to narcotic 

 and sedative poisons ; ammonia for example being correctly prescribed in 

 prussic acid poisoning, strvchnine as a nerve stimulant in snake-bite and 

 atropine in tobacco poisoning. Opium, chloral hydrate, conia and other 

 sedatives are used as phvsiological antidotes in poisoning by irritants or 

 stimulants. 



MINERAL POISONS. 



Arsenic Poisoning. 



There has been at various times very great mortality amongst stock in 

 the vicinity of pyrites works due to poisoning by arsenic. In the roasting 

 of the ore, arsenic in the form of arsenious oxide (As2 O3) is driven off and 

 if its escapee is not prevented by condensation at the w^orks it is deposited 

 on the surface of the ground in the vicinity. The herbage becomes coA-ered 

 with a layer of arsenical dust, and when eaten by stock, arsenic poisoning 

 results. Of course the greatest deposition occurs immediately adjacent to 

 the works where the herbage, shrubs and trees may be completely destroyed. 

 Creek waters may be impregnated to such an extent as to give rise, on 

 drinking, to symptoms of poisoning. In the direction of prevailing winds, 

 however, the fumes may be carried a considerable distance and the danger 

 of stock poisoning, even upwards of a mile awav, mav he evidenced by 

 the sickly paleness of the grass and the " pitting " and shrivelling of young 

 leaves of trees in exposed situations. 



In 1898 I undertook an investigation regarding an allegation of wide- 

 •spread poisoning of stock by arsenic on one of the smaller Victorian 

 goldfields. On a common on which pyrites smelting w^orks w-ere situated 

 forty-one horses and eighty-one cattle (total stock 122) had died 

 at different periods during the previous twelve months. All the lambs 

 born on the common during the vear had died, and out of a flock of forty 

 sheep, placed there in the belief that they would withstand the arsenicated 

 herbage, fifteen died. A numter of turkeys and fowls also died in 

 the vicinity of the works. The investigation resulted in bringing to light 

 convincing evidence that the majoritv of these deaths had been directly 

 caused by arsenic poisoning. Some of the victims succumbed to an acute- 

 attack and others were affected chronicallv. One resident lost eleven head 



