Mastering the quantity of each herb used is very important in clinical practice. This is especially so when we want to practice prescribing 经方 i.e. those created by Mr. Zhang Zhongjing.
桂枝汤 as an example:
In 桂枝汤, 3 liang each of 桂枝 and 芍药 are used, and the function of 桂枝 is to 解肌祛风、调和营卫.
- If we increase the quantity of 桂枝 – as in 桂枝加桂汤 where 5 liang of 桂枝 is used – its purpose is to 温补心阳、降逆平冲 as treatment for the running piglet pattern.
- If we increase the quantity of 芍药 instead – as in 桂枝加芍药汤 – the decoction’s purpose is to treat intrusion on the taiyin spleen channel that causes 气血不和-type of abdominal pain（腹满时痛）.
Yes, you say, in the latter decoction, the key herb is no longer 桂枝 but 芍药, and it’s 芍药 that helps to take away the pain. One can even infer further that treatment of such pain is limited to the 桂枝-type person. As for the former decoction, the additional 桂枝 just turns up the heat on the lower jiao in addition to helping the heart, all in all eliminating further activity by the piglet.
麻黄汤 as an example:
Again, the ratio of 麻黄：桂枝：甘草 should be 3:2:1, otherwise you’ll probably spend all day trying to get the patient to perspire.
五苓散 as an example:
The herb used in the largest quantity here is 泽泻, while 桂枝 just plays a minor role. If used as presribed in the ancient texts, this formula has a diuretic effect. Interestingly, when all five component herbs are used in equal portion, the diurectic effect is no significant. Obviously, that’s because we now know 泽泻 to be a diuretic, and of course it has to be the main player here.
We’ve only covered ratios above, which most people won’t have a problem with. The more important question becomes “how many grams of each herb do I put in?” We have to understand that Mr. Zhang was living in the Han era, and the Han era didn’t measure in grams or units we use today. If the chinese measurements of qian and jin could have been different in that era.
And it was.
Checking out the Han era books:
Checking up 《汉书·律历志》, which reflects measurement norms in the Han era, we see the following phrase:
meaning 1200 grains of rice is 12 zhu (unit of measurement) and two 12 zhu is one liang. Hence 24 zhu is 1 liang. Which tells us that the most fundamental unit was zhu and we used rice grains to determine that. Which also tells us that the unit of measurement liang is 24 zhu.
The book continues…
informing us that 16 liang is one jin, and 30 jin is one jun, and 4 jun is one shi.
Overall, we’re set, we just need to find those grains of rice and count 1200 of them. But from where? Beijing, Changsha, from the sack, fresh from harvest? So there’s an issue here. But luckily, we needn’t go through all that trouble, because in the museums are heavy bronze pieces of different units of measure, and that includes one that says 1 jin and when we weigh that something, we realize that it’s 250g. So easy.
And so, using the original text once again, we can deduce that if 1 jin is 250g, then 1 liang is 250/16 = 15.625g. Let’s approximate 1 liang at 15g then.
Let’s now move on to volume measurements:
If you put 1200 grains into a container, that container contains one yue. So the smallest volume measurement is called yue. Two yue is one ge. And so on.
We go back to the museums and find out that One ge is 20ml. One sheng is 200ml. One dou is 2,000ml. One hu is 20,000ml (you can actually find a big hu in the Shandong Museum).
It seems that there’s no problem at all when there are artifacts to tell us exactly what was. We can then re-measure them using contemporary units of measure.
Now, we understand what eight ge means, we realize the book is exhorting us to drink 8 times 20ml of Ephedra Decoction, which is a total of 160ml. Great! And for Cinnamon Twig Decoction, it would be one sheng which equals 200ml. Eureka! Same with 麻杏石甘汤,which is one sheng, and the text adds “温服一升，本云黄耳杯” meaning that the yellow-earred cup（黄耳杯）approximates one sheng. And when if we go to the museum and check, voila, it is!
Before and after the Song dynasty:
Up till the Song dynasty, most practitioner would use the units of measure delineated above. There were changes, especially between the Jin and Song dynasty (a period of about 800 years), however the units of measure remained the same. After the Song dynasty, because the government brought about many changes, you’ll see the following units of measure: 斤、两、钱、分、厘、毫. So that’s a way to recognize whether the manuscript you’re reading is before or after the advent of the Song dynasty.
Later on though, in the modern era, the Chinese converted 1斤=500g, but this didn’t affect how chinese practitioners calculated herbal quantity. 1钱 was still about 3g, and so 3钱 was about 9g. And since 9g is close to 10g, that’s why we see so many 10g herbs in prescriptions these days. A typical quantity at that time was 3钱, which is approximate 10g today.