The activities of the several human organisms in relation to the organism as a whole are strikingly expressed in the formation of the blood and nerves. Where the foodstuffs absorbed into the body become progressively transformed in the process of blood-formation, this whole process stands under the influence of the ego-organization. From the processes that take place in the tongue and palate, accompanied by conscious sensation, down to the unconscious and subconscious processes in the workings of pepsin, pancreatic juice, bile, etc., the ego-organization is at work. Then the working of the ego-organization withdraws, and in the further transformation of foodstuffs into the substance of blood, the astral body is predominantly active. This continues to the point where, in the breathing process, the blood meets the air, the oxygen. At this point the etheric body carries out its main activity. In the carbonic acid that is on the point of being breathed out but has not yet left the body, we have a substance which is in the main only living that is to say, it is neither sentient, nor dead. (Everything is alive that carries in it the activity of the etheric body.) The main quantity of this living carbonic acid leaves the organism; a small part continues to work into the processes that have their centre in the head organization. This portion shows a strong tendency to pass into the lifeless inorganic nature, but it does not become entirely lifeless.
The nervous system shows an opposite phenomenon. In the sympathetic nervous system which permeates the organs of digestion, the etheric body is paramount. The nerve organs with which we are here concerned are primarily living organs. The astral and ego-organizations do not organize them from within but from without. For this reason the influence of the astral and ego-organizations working in these nerve-organs is powerful. Passions and emotions have a deep and lasting effect upon the sympathetic nervous system. Sorrow and anxiety will gradually destroy it.
The spinal nervous system, with its many ramifications, is the one in which the astral organization primarily intervenes. Hence it is the bearer of everything which is psychological in man, namely the reflex processes, but not of that which takes place in the ego, in the self-conscious spirit.
It is the actual cranial nerves which underlie the ego organization. In these, the activities of the etheric and astral organization withdraw.
We see three distinct regions arising in the organism as a whole. In a lower region, nerves permeated from within mainly by the action of the etheric organism work with a blood substance that is predominantly subject to the activity of the ego-organization. In this region, during the embryonic and post-embryonic period of development, we have the starting-point for all organ-formations connected with the giving of inner life to man's organism. In the formation of the embryo, this region, being weak as yet, is supplied with formative and life-giving influences by the surrounding maternal organism. Then there is a middle region, where nerves, influenced by the astral organization, are working with blood-processes which are likewise dependent on this astral organization and, in their upper parts, on the etheric. Here, in the periods of formation of man, lies the starting point for the formation of those organs which are instrumental in the processes of outer and inner movement, this applies not only to the muscles for example, but all organs which are causes of mobility, whether or not they be muscles in the proper sense. Finally there is an upper region where nerves, subject to the inner organizing activity of the ego, work with blood-processes that have a strong tendency to pass into the lifeless, mineral realm. Here lies the starting point, during man's formative epoch, for the formation of the bones and all else that serves the human body as organs of support.
We shall only understand the brain of man if we see in it a bone-forming tendency interrupted in its very first beginning. And we shall only understand the bone formation when we recognize in it the working of the same impulses as in the brain; in the bone formation, the brain-impulse is carried to its final conclusion and permeated from without by the impulses of the middle organism, where astrally determined nerve-organs are working together with blood-substance etherically determined. In the bone-ash which remains with its particular configuration when the bones are subjected to combustion, we see the results of the uppermost region of the human organization. While in the cartilaginous organic residue which remains when the bones are treated with dilute hydrochloric acid, we have the result of the impulses of the middle region.
The skeleton is the physical image of the ego-organization. In the bone creating process the human organic substance, as it tends toward the lifeless mineral, is entirely subject to the ego-organization. In the brain, the ego is active as a spiritual being. The capacity of the ego to create form in the physical substance is here overwhelmed entirely by the organizing activity of the etheric, even by the forces proper to the physical. The brain is based only minimally on the ego's organizing power, which here becomes submerged in the processes of life and in the workings of the physical. Yet this is the very reason why the brain is the bearer of the spiritual work of the ego. For, inasmuch as the organic and physical activities in the brain do not involve the ego-organization, the latter is able to devote itself freely to its own activities. In the bony system of the skeleton, perfect though it is as a physical picture of the ego-organization, the latter exhausts itself in the act of forming and organizing the physical, and as spiritual activity, there is nothing left. Therefore the processes in the bones are the most unconscious
So long as it is in the organism, the carbonic acid which is pushed out in breathing is still a living substance; it is taken hold of and driven outward by the astral activity that has its seat in the middle or spinal region of the nervous system. The portion of carbonic acid which the metabolism carries up into the head is there combined with calcium, and thus develops a tendency to come into the sphere of action of the ego-organization. Through this, calcium carbonate is driven under the influence of the head nerves, motivated inwardly by the ego-organization, toward bone-formation.
The substances myosin and myogen produced out of the foodstuffs, tend to become deposited in the blood; they are substances astrally conditioned to begin with, and they stand in reciprocal interaction with the sympathetic, which is organized from within by the etheric body. These two proteins are, however, also taken hold of to some extent by the activity of the middle nervous system which is under the influence of the astral body. They thus come into relationship with the breakdown products of albumen, with fats, sugar, and other substances similar to sugar. This enables them, under the influence of the middle nervous system, to find their way into the process of muscle-formation.