Page:Scientific Memoirs, Vol. 1 (1837).djvu/260

248 development of the organs of generation,) is united by means of the stem to the root, which is held in connexion with the organism of the earth. It is also remarkable, that in the fœtus the direction of the development from the insertion of the umbilical cord is upwards, as we see in the plant that the flower is directed upwards from the insertion of the stalk. For instance, the anthers are never turned back toward the stem and the fruit-germ, or directed downwards, but on the contrary are invariably and wholly directed upwards, unless the flower-stalk and fruit-germ are turned downwards, in which case they also are directed downwards with them. This explains the development of the vertebral column into the head, in which the flower of the collected animal organization appears as completely as the flower of the egg does in the entire fœtus. This fact is still more clearly observable in the central structure of the vertebral column, viz. the spinal marrow, the fibres of which we see more perfectly developing themselves as they ascend upwards, till they terminate in the perfect and noble formation of the brain.

This direction of development in the fœtus, the truth of which is most clearly established by many physiological as well as pathological observations, is also indicated by the position of the entire fœtus, in which we find the head usually turned downwards, but the lower extremity turned toward the insertion of the umbilical cord; in the same manner as the flower of the plant, and the head of the more perfect animal, rise upwards from the ground. Moreover, that the greater weight of the head which occasions it to sink downwards in the uterus is not the only use of that position of the foetus, is evident from the parturition of the quadruped mammalia, since although their standing on four feet must prevent the operation of such a cause, they nevertheless bring forth their young with the head (nay even with the face) forwards.

We can here give but general outlines of the further development of the different systems and organs formed in the fœtus; and with respect to the systems belonging to the animal side of the animal body, and which corresponds to the light side of the plant, we observe that from their constituting the parts originally turned toward the outer world, they are endowed with a tendency to develop their structure in a direction radiating outwards from an internal centre; for which reason we see the nervous system form itself as the radii of a central mass (the brain and the spinal marrow), which develops itself with a perfection continually increasing in proportion as the radiation outwards increases; we see also the ends of the nerves forming themselves either into the organs of sensation, or, as being destined to re-act upon external objects, inserting themselves into the molecular mass of the animal; so that these molecules, disposed into muscular fibres, are drawn, sometimes more and sometimes less