POINT TO POINT 



6213 



POISON 



On either side of the crossing, on 

 the inner edges of the two outer 

 rails, a short length of guard rail 

 is fixed, to prevent the flanges from 

 fouling and mounting the frog. Tn 

 cases where the track branches into 

 three it is termed a three-throw 

 switch ; the arrangement is more 

 complicated as additional tongue 

 rails are introduced. When a frog 

 points in the direction from which 

 trams approach, the switch is 

 a facing switch ; when in the 

 opposite direction, a trailing switch. 



The curvature of rails at a turn- 

 out is determined by the angle of 

 crossing, i.e. the angle at which the 

 switch-rails would cross, measured 

 on the gauge line, if not splayed 

 at their ends. The greater the 

 angle the sharper the curvature ; 

 both are determined by the gauge 

 of the railway, the speed at which 

 trains have to be diverted, and 

 other considerations. See Railways. 



Point to Point. Name given to 

 a type of race for hunters. They 

 are held under the auspices of a 

 hunt, and are usually divided into 

 two classes : for welter-weights, 

 over 13 stone, and for light-weights 

 under that figure. Usual con- 

 ditions are that the horses entering 

 must have been regularly hunted, 

 and must be ridden by their owners. 

 The course is generally one of three 

 or four miles, over a fair hunting 

 country. See Steeplechasing. 



Poire, EMMANUEL. Real name 

 of the French caricaturist better 

 known by his pseudonym of Caran 

 d'Ache (q.v,). 



Poison (Lat. potio, draught). 

 Substance which, when taken into 

 the mouth or stomach or absorbed 

 by the blood, is capable of seriously 

 affecting health or destroying life. 

 Some poisons have a local action 

 only, as the strong mineral acids 

 which injure the tissues with which 

 they come directly in contact. 

 When well diluted they are not 

 poisons. Other poisons, e.g. mor- 

 phia, have no local action, and only 

 produce symptoms after having 

 been absorbed into the system. 



A poison which is inhaled in 

 the form of a gas, or is injected 

 hypodermically straight into the 

 blood stream, acts with great ra- 

 pidity. When swallowed, absorp- 

 tion is much less rapid, and as the 

 process of elimination acts con- 

 currently, an amount taken by the 

 mouth may be less dangerous than 

 a smaller amount injected sub- 

 cutaneously. Poisons may also be 

 absorbed through the skin. Some 

 poisons, as alcohol, morphia, and 

 cocaine, when taken for a long 

 period, gradually confer on the 

 taker a degree of tolerance which 

 enables him to swallow quantities 

 which would normally be fatal. 



In the treatment of poisoning, 

 the first object aimed at is removal 

 of the poison from the system. 

 Vomiting may be produced by 

 tickling the back of the throat 

 with a feather, or by the adminis- 

 tration of an emetic, as a table- 

 spoonful of mustard, or one or 

 two tablespoonfuls of salt in a 

 tumbler of warm water. This 

 form of treatment may be em- 

 ployed in all cases of poisoning, 

 except those due to the strong 

 mineral acids or to strong alkalis, 

 in which straining the damaged or 

 corroded tissues may lead to per- 

 foration of the stomach. The 

 treatment for strong acid poison- 

 ing is to adminster an alkali, cal- 

 cined magnesia being the best ; but 

 in an emergency sodium bicar- 

 bonate, chalk, or even plaster 

 from the ceiling may be given, and, 

 failing these, the poison should 

 be diluted by administering large 

 draughts of water. 



In poisoning by caustic potash 

 or other alkalis, water with 

 vinegar or lemon-juice should be 

 given to neutralise the acid. An- 

 other method of removing poison 

 is by means of the stomach-tube. 

 A long, flexible indiarubber tube is 

 passed by the physician into the 

 stomach, and the tube and stomach 

 are then filled with water through 

 a glass funnel. By lowering the 

 funnel, the fluid is drawn off from 

 the stomach by syphonage. Thus 

 the stomach can be washed out as 

 frequently as necessary, and anti- 

 dotes introduced. With such 

 poisons as fungi, in which the on- 

 set of the symptoms is delayed for 

 several hours, much of the poison 

 is apt to have passed on from the 

 stomach into the intestines, and in 

 these cases administration of a 

 brisk purge assists elimination. 



Use of Antidotes 



Antidotes to poisons act in 

 various ways. The object in some 

 cases is to convert the poison into 

 an insoluble substance. Thus, hi 

 oxalic acid poisoning, soluble cal- 

 cium salts are given to precipitate 

 the insoluble calcium oxalate. 

 In poisoning by metallic salts, 

 such as the corrosive sublimate 

 or mercuric chloride, albuminous 

 substances such as white of egg are 

 useful, as they convert the poison 

 into albuminates, which are much 

 less soluble. These, however, are 

 slowly digested, so that it is still 

 necessary that they should be 

 removed from the system by emesis 

 or washing out. Other antidotes 

 act as physiological antagonists, 

 i.e. they produce the opposite 

 effect of the poison. With signs 

 of heart failure, ether, strychnine, 

 or caffeine may be administered. 

 Respiratory failure may need treat- 



ment by artificial respiration. Pro- 

 longed vomiting and severe pain 

 may justify the use of morphia. 



Poisoning by vegetable food, 

 with the exception of fungi, is 

 rare, occurring almost exclusively 

 as a result of accidental contamina- 

 tion of the food, as, for example, 

 when lead is dissolved out of the 

 vessel containing preserved fruit 

 by the action of the fruit juices. 



MEAT. Poisoning by meat is 

 nearly always the result of acute 

 infection by bacteria, following 

 the eating of diseased or putrefying 

 meat. Usually, the animal from 

 which the meat has been pre- 

 pared has been found to be suffer- 

 ing from infection with the Bacillu-s 

 enteritidis of Gartner, an organism 

 which belongs to the paratyphoid 

 group. The disease has been found 

 in cows after septic poisoning fol- 

 lowing calving. Less frequently, 

 it has occurred in sheep and pigs. 



Botulism is a rare form of poison- 

 ing due to the presence of a micro- 

 organism, which has been found 

 in infected meat that has been 

 potted, or otherwise preserved so 

 as to exclude air. 



Symptoms of Meat Poisoning 

 The symptoms of poisoning from 

 meat usually begin from 6 to 12 

 hours after the food has been eaten. 

 Sometimes there is a delay of 

 from 12 to 48 hours. They may 

 begin suddenly with acute onset, 

 or more gradually with nausea, 

 loss of appetite, and feelings of ill- 

 health. The most marked symp- 

 toms are vomiting, pain, or colic 

 in the abdomen, headache, pro- 

 fuse diarrhoea, pain in the back, 

 and rise of temperature. Rashes on 

 the skin sometimes occur, and, in 

 severe cases, delirium. The great 

 majority of cases recover, but in 

 severe cases there may be failure 

 of the action of the heart, collapse, 

 and death. When the symptoms 

 begin early, some relief may be 

 obtained by inducing the patient 

 to vomit ; but usually the food 

 has passed on from the stomach 

 before the condition is recognized. 

 Any decomposing fish may give 

 rise to poisoning. Mackerel is es- 

 pecially liable to become rapidly 

 unfit for food. Crabs, lobsters, and 

 other shellfish are equally dan- 

 gerous if not fresh. Oysters and 

 mussels, if they have grown in 

 sewage-polluted waters, may con- 

 vey typhoid. The symptoms are 

 those of irritation of the stomach 

 and intestines. Milk may be re- 

 sponsible for epidemic poisoning, 

 if infected by organisms. It may 

 also convey diphtheria and other 

 bacterial diseases. 



The Pharmacy Acts impose cer- 

 tain restrictions on the sale of 

 poisons. The poisons to which the 



