Doctors used special ways to weigh medicine. 
Doctors and medicine makers used special weights. 
They used parts of a pound. One pound could be split into many small pieces. These pieces had names like ounces and grains.
This system was very old. It came from the ways of the Romans. 
They also measured liquids. They used a unit called a fluid ounce. They even used tiny drops.
Most people do not use these weights now. They use a new system called metric instead.
Long ago, doctors and pharmacists used a special way to measure medicine. This was called the apothecaries' system. 
This system used different names for weights. A pound was split into many small parts. These parts included ounces, drachms, scruples, and grains. 
They also measured liquids. They used a unit called a fluid ounce. To measure tiny amounts, they used drops. A drop was often just a single drop from a bottle.
In the past, different places used different rules. This could be very confusing for trade. In 1850, Ireland tried a new way to fix this. They wanted to match the weights used for buying goods. Later, the United Kingdom and the United States changed everything. They switched to the metric system in 1971. Now, most people use metric units for medicine instead.
Doctors and pharmacists once used a special way to measure medicine. This was called the apothecaries' system. It helped them be very exact with every dose. 

Measuring medicine requires many small steps. The system broke a large pound into smaller parts. One pound was divided into twelve ounces. Each ounce was split into eight drachms. A drachm was then divided into three scruples. Each scruple was made of twenty grains. 
This way of measuring has a very old history. The units came from the ancient Roman weight system. Famous Greek doctors like Galen and Dioscorides helped pass these ideas down. They lived in the 1st and 2nd centuries. Their writings were very influential for many years.
Different rules existed in different places. In the 19th century, many European cities had two systems. One was for general trade and one was for precious metals. In 1850, Ireland tried a new plan. They wanted to use the avoirdupois pound instead of the troy pound. This was meant to make buying and selling easier. 
Today, most people do not use these old units. The United Kingdom and the United States both changed. They moved to the metric system in 1971. This made measurements the same in many countries.
The apothecaries' system was a specialized set of units used to measure mass and volume. It was primarily used by physicians and apothecaries for medical prescriptions. Scientists also utilized this system for their work. It provided the precision necessary for preparing medicinal substances. This system was not just for weight, but also included volume measurements for liquids. 
To understand how the system worked, one must look at its subdivisions. The traditional English apothecaries' system was based on the troy pound. This pound was divided into 12 ounces. Each ounce was further divided into 8 drachms. A drachm was split into 3 scruples. Finally, each scruple consisted of 20 grains. 
This system also included a way to measure liquid volume. These units were often called fluid measures. A fluid ounce was a volume approximately equal to an apothecaries' ounce of water. This fluid ounce could be divided into fluid drachms. Sometimes, these were further divided into fluid scruples. 
The history of these units reaches back to antiquity. The apothecaries' system was a subset of the Roman weight system. It was inherited through influential medical treatises. These writings were produced by Greek physicians such as Dioscorides and Galen. They lived during the 1st and 2nd centuries.
In the 19th century, many regions faced confusion due to overlapping systems. Most European cities used a "commercial" or "civil" system for general trade. An example is the English avoirdupois system. However, they used a second system, like the troy system, for precious metals. The apothecaries' system was closely related to the troy system. For example, the pound and grain were exactly the same in both. 
Several attempts were made to unify these different standards. In 1850, an innovation was proposed in Ireland. The Irish College suggested replacing the troy pound with the avoirdupois pound. They wanted to align the units used for sales with the units used for purchases. This proposed system used 16 ounces per pound. It would have changed the value of the drachm significantly. 
Legislative changes eventually led to the system's decline. The British Medical Act of 1858 was a radical step. It prescribed the use of the avoirdupois system for the United Kingdom. This included the use of the imperial avoirdupois pound, which contained 7,000 grains. The traditional subdivisions like the drachm and scruple were eventually discontinued in official pharmacopoeias. 
The system eventually became obsolete in many parts of the world. In the United Kingdom, the Weights and Measures Act 1976 restricted its use. It could then only be used for precious metals and stones. In both the United Kingdom and the United States, the metric system became mandatory. This change occurred in 1971.
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