Commentary on the Sūtra of the Collection of the Father and Son (Pitāputrasamāgamanasūtra) (37)

The Bacteria Within the Sentient Body

The element of fire has the nature of heat and warmth. If there were no fire-nature and temperature within the body, the food in our stomachs could not decompose and be absorbed by the body. Therefore, no matter how delicious the food and drink we eat, no matter how complete their color, fragrance, and flavor, once they enter the stomach, the fire-nature in the body rots the food. The food and drink we consume, the so-called nutrients we absorb, are extremely filthy and impure; thus one should not crave food and drink. By frequently engaging in this contemplation of impurity, one can reduce the craving for food and drink.

In fact, upon careful reflection, our bodies, from top to bottom and from inside to outside, are extremely filthy, covered with bacteria everywhere. The decomposition of food relies entirely on the bacteria's breaking down of what we eat. Without the help of bacteria, we could not absorb food. It is the bacteria that help us decompose, digest, and absorb; sentient beings can live normally only by relying on these beneficial bacteria. Therefore, there is no need to crave and be infatuated with our own filthy physical bodies, or with the filthy physical bodies of other sentient beings.

The Buddha said that the physical body of a sentient being is like a mobile toilet, a large manure bucket, wrapped in a layer of smooth outer skin. If you peel off this outer skin, inside it is a bloody, mangled mess, full of bacteria, and even the outer skin is teeming with bacteria. When the skin is peeled off, is this person still pretty and beautiful? It is all flesh and blood, sinews, and bones. Upon careful reflection, the physical body of a sentient being truly has nothing worth clinging to or craving—it is extremely filthy. If we had the divine eye, with our eyes functioning like a microscope to examine our skin and the interior of our body, we would find that inside and out everything is bacteria—something our naked eyes cannot see, but which a microscope and the divine eye can see. Those bacteria are also fighting among themselves. When the bacterial population becomes unbalanced, skin diseases and other illnesses arise; wherever the bacterial population is unbalanced, there is disease there. When we feel hungry, it is also because the bacteria are hungry: when the bacteria want to eat, we want to eat, and thus we become gluttonous and greedy for food.