The related lecture text explains the correlation. The noblest instrument possessed by the human being is said to be its “Blood,” which is the instrument of its Ego. Before any sort of nutrient can be taken in from the plant or animal kingdoms, which have their own rhythms, its rhythm must be modified to correspond with the human rhythm. The digestive organs involved in this process are the spleen, gall bladder and liver, whose main collective function is to repel what constitutes the particular inner nature of this food. These organs thus adapt the laws of the outside world, from which we take our food, to the inner organization or rhythm of the human being. There must, however, be a continual living reciprocal activity of the human being with the outside world, though these three organs are placed in opposition to it. What is thus fed into the “Blood” (Ego) system must be balanced by what represents the outside world. This is accomplished by the lung system through which oxygen enters the “Blood” directly from the outer world, assisted by the kidney system. Thus, we have the spleen-liver-gallbladder (inner) system balanced by the lung-kidney (outer) system. The blood system (Ego) with the heart as its central point is placed in the middle where these two opposing systems are brought into balance for the sustenance of the human being.

It can be seen that the outer planets are associated with what comes from food and the inner two planets with what comes from air and “Blood” purification. Just as the Ego, in its spiritual connection, presupposes the physical, etheric and astral bodies, so also the physical blood-system (Ego), in its physical side, presupposes these two counterbalancing systems, portrayed as follows:

There is a further powerful indication of these relationships. In I-27 we saw the relationships of the various metals to the planet from which they originated. We now see that where one of the above organisms manifests too strong an inner vitality, it must be counterbalanced, which can be brought about by a proper application of these metals (which is beyond our present scope). We thus see the outer cosmic system duplicated in our inner cosmic system.

This is not the only manifestation of the planetary system in our earthly being. Another one, for instance, is that set out in I-21 where the planets are shown to have a relationship to the seven “lotus flowers” (Pineal, Pituitary, Larynx, Heart, Solar Plexus, Kidney, Reproductive). Another is the relationship between the number of spinal vertebrae and days in the monthly cycle of the Moon. In RMI, Lect. 5, Steiner numbers the vertebrae at 28 to 30. While trying to get a better fix on the number, it is also fascinating to distinguish (see 24 Brit 810, “The Spinal Cord,” and 815, “Spinal Nerves,” “Nerves and Nervous Systems”) between vertebrae and spinal nerves (see I-20), as follows:

However, the Coccygeal vertebrae are described as “vestigial” and as “rudimentary and occasionally absent,” so they would not seem to be of significance in this count. If they are eliminated, the total vertebrae count is 29, which corresponds approximately to the 27 1/2 days in the lunar month, the median (between 29 and 27 1/2) being close to 28, a number divisible by the planetary seven. Thus our bony skeleton relates primarily to the Moon forces, while the higher nervous system relates more closely to the 30+ days derived by dividing the year by the zodiacal Twelve. Steiner sketched (RMI, Lect. 5) the following illustration of how the ancient initiates saw in the formation of the human spine a copy of the monthly movement of the Moon, “of the streams that the Moon sends down continually upon the Earth”: ^{(click here for illustration)}