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Full text of "Medical Jurisprudence And Toxicology"

632                                               MEDICAL JURISPRUDENCE

stomach full of food. Alcohol reaches its maximum concentration in the
blood within approximately an hour and a half after it is taken, and this
concentration is ordinarily proportional to the amount consumed. After
absorption, alcohol is distributed almost uniformly in all the organs and
tissues except fat and bone, but the rise and fall in its concentration is
slower in the brain, spinal cord and cerebrospinal fluid than in the blood
and other tissues. It disappears very slowly, so that it is found in the blood
for about twenty hours after it is drunk.7 Over 95 per cent of the alcohol
ingested is oxidized to carbon dioxide and water, and the remaining portion
is eliminated unchanged mainly by the lungs and kidneys. It has been
ascertained that alcohol appears in the urine within half-an-hour of its
ingestion.8

There is close relationship between the concentration of alcohol in the
blood and the degree of alcoholic intoxication. Carter and Southgate9
have also demonstrated that the concentration of alcohol in the urine is
proportional to that of the blood under all conditions, and that the mean
ratio of alcohol in the urine to alcohol in the blood one hour after taking the
alcohol is 1.35. Hence it is necessary to analyse the blood or urine for the
estimation of alcohol concentration in cases where persons have been accused
of being drunk while creating disturbance in streets or driving motor cars.

It must, however, be remembered that the examination of urine for the
determination of alcohol is more advantageous, 'inasmuch as the alcohol
concentration in urine is more constant than that in the blood which is likely
to vary owing to its oxidation in the tissues. Certain substances such as
acetone, ether, paraldehyde, etc. are at times present in the blood, and are
likely to be determined as alcohol, and thus vitiate the test. Besides, it is
much easier to obtain a sample of urine than that of blood for examination.

i Evans and Jones10 have shown that the concentration of alcohol in urine
[1 is so precise that it gives an accurate indication of the minimum quantity of
alcohol consumed. They have also shown that the consumption of one fluid
ounce of whisky under the most favourable conditions gives a maximum
concentration of 0.024 per cent alcohol in the urine, while the consumption
of a pint of beer will give a concentration of 0.037 per cent. Thus, a con-
centration of 0.3 per cent alcohol in the urine means the consumption of at
least 12J fluid ounces of whisky or 8 pints of beer.

It is generally believed that persons with a concentration of 0.1 per cent
alcohol in the blood appear to be gay and vivacious, and those with a con-
centration of 0.15 per cent alcohol in the blood are regarded as fit to drive
a motor vehicle. This concentration of alcohol in the blood is regarded as
a presumptive limit of safety, and may result from the rapid consumption
of 8 ounces of whisky or 4 to 5 pints of beer. Persons with a concentration
of 0.2 per cent alcohol in the blood show symptoms of moderate intoxication,
those with from 0.2 to 0.4 per cent are probably drunk and those with more
than 0.5 per cent are dead drunk or deeply comatose. When the amount of
alcohol approaches 0.6 to 0.7 per cent or more in the blood death usually
ensues from asphyxia. It is legal offence for a person to drive a motor
vehicle with a blood alcohol level above 0.05 per cent in Norway, above 0,08
per cent in Sweden, and above 0.10 per cent in Denmark.

7.   Mellanby, Brit. Medical Research Council, Special Report Series No 31

8.   Carter and Southgale, Transactions, Med-Legal Society, Vol  XX. p. 44

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