The activity of the nervous system is essential for extra-uterine life; life ceases by the cessation of circulation and respiration when either the whole or certain small areas of its tissue are destroyed.

In intra-uterine life, with the narrow and unchanging environment of the fluid within the uterine cavity which encloses the foetus, life is compatible with the absence or rudimentary development of the nervous system.

The foetus in this condition may be otherwise well developed, and it would be not a misuse of words to say that it was healthy, since it is adjusted to and in harmony with its narrow environment, but it would not be normal.

The intra-uterine life of the unborn child, it must be remembered, is carried out by the transmission of energy from the mother to the foetus by means of the close relation between the maternal and foetal circulation.

It is only when the free existence demands activities not necessary in intra-uterine life that existence without a central nervous system becomes impossible.
It is essential in so complicated a structure as the body that some apparatus should exist to provide for the interchange of material.