THE WONDERS OF LIFE 



omission.** It punishes abortion with several years' 

 imprisonment. But while civil law thus takes its in- 

 spiration from canon law, it overlooks the physiologi- 

 cal fact that the ovum is a part of the mother's body 

 over which she has full right of control; and that the 

 embryo that develops from it, as well as the new-born 

 child, is quite unconscious, or is a purely "reflex ma- 

 chine," like any other vertebrate. There is no mind in 

 it as yet ; it only appears after the first year, when its 

 organ, the phronema in the cortex, is differentiated. 

 This interesting fact is explained by the biogenetic law, 

 which shows that the ontogeny of the brain is a con- 

 densed recapitulation of its phylogeny in virtue of the 

 laws of heredity. 



The biogenetic law applies just as much to the brain, 

 the organ of mind, as to any other organ of the human 

 body. On the strength of the ontogenetic facts, which 

 fall under direct observation, we infer that there was a 

 corresponding development in the phylogenetic series of 

 our animal ancestors. A significant confirmation of this 

 inference is found in comparative anatomy. It shows 

 that in all the skull-animals (craniota) — from the fishes 

 and amphibia up to the apes and man — the brain is 

 developed in the same way, as a vesicular distension of 

 the ectodermal medullary tube. This simple oval cere- 

 bral vesicle first divides into three and afterwards five 

 successive vesicles by transverse constriction (Anthro- 

 pogeny, chapter xxiv., plate 24). It is the first of these 

 vesicles, the cerebrum, that afterwards becomes the 

 chemical laboratory of the mind. In the lower craniota 

 (fishes and amphibia) the cerebrum remains very small 

 and simple. It only reaches a notably higher stage in 

 the three chief classes of the vertebrates, the amniotes. 

 As these land-dwelling and air-breathing craniota have 

 more difficult work to do in the struggle for life than 

 their lower aquatic ancestors, we find much more varied 



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