326 ACIDS ACIDA 



tannic, and hydrocyanic acids differ chemically and physio- 

 logically, and will be dealt with separately. 



Acids are hydrogen salts which in presence of an alkali 

 exchange for it their hydrogen, or a portion of it. They 

 redden various blue and violet colouring matters, and most 

 have a sour taste. In virtue of their affinity for basic sub- 

 stances and for water, acids, especially when concentrated, 

 form new compounds with the animal tissues. Their primary 

 effects are (1) to unite with and neutralise the free alkali 

 which is present in most normal tissues, thus acting as proto- 

 plasmic poisons ; (2) the stronger often displace weaker 

 acids ; (3) they precipitate albumin, while all the mineral 

 acids, except nitric, again dissolve albumin. When intro- 

 duced directly into the blood, they, moreover, destroy the 

 red cells, decompose haemoglobin, forming methsemoglobin, 

 a substance which parts with oxygen much less readily. 

 They coagulate myosin, and hence cause muscular rigidity, 

 whilst even one in twenty thousand lessens the height of 

 a muscle contraction. The stronger acids, especially when 

 concentrated, are caustics and escharotics. Weaker and 

 more diluted acids act as rubefacients, cause temporary 

 congestion, and, if freely or continuously applied, inflame the 

 dermis, producing vesication. They destroy enzymes and 

 check proliferation of organised ferments, in proportion to 

 their acidity. 



Acids, when swallowed, are corrosive, irritant poisons. 

 As with other irritants, they are more active and fatal in 

 horses and dogs than in cattle or sheep, in which their toxic 

 effects are diminished by admixture with the bulky food 

 usually present in the stomachs of these ruminants. ' In 

 cases of acute poisoning, where death has not occurred too 

 quickly, much albumin, hsematin, and indican have appeared 

 in the urine, and fatty degeneration of the liver, muscles, and 

 kidneys has been found ' (Sir Lauder Brunton). Their ap- 

 propriate antidotes are alkaline bicarbonates, or calcium and 

 magnesium carbonates, given with such diluents and demul- 

 cents as milk, oil, and linseed gruel, and followed by opium 

 and fluid nutrients. 



Acids in the mouth reflexly increase the saliva from the 

 parotid and submaxillary glands, and effectually moisten the 



