ON EMBRYONIC DIFFERENTIATION 265 



In this way is obtained and maintained a physio- 

 logically even employment of the dual organisms, and 

 energies, a graduated activity of all parts of the organism,, 

 and a mean, or healthy, biological result, in other words a 

 mem sana In corpore sano the desideratum of desiderata. 



The anterior limb, of the neurenteric V, becomes 

 subservient to the purposes of the sympathetic nervous 

 system, the two limbs being united, and held together, 

 in their common work, by the inter-agency of a common 

 blood circulation. 



In the following remarks on this subject, we shall deal 

 mostly with the enteric division of the canal. During 

 embryonic, and intra-uterine, existence, the range of func- 

 tional activity of the enteric canal, is necessarily restricted 

 to that, involved in its comparatively passive condition, of 

 preparation for the coming lactation duty, of digesting the 

 carefully elaborated, mammary secretion, and, therefore, 

 at birth, its contents are composed of only the exfoliated 

 residuum of organic waste, enteric, and neural. The 

 enteric canal, during this period, undergoes a gradual 

 evolution from a comparatively straight and plain tube, 

 into a multi-duplicated canal, the walls of which are inter- 

 penetrated and surrounded, by glandular developments, 

 and elaborate secreting organs, to fit it for the perform- 

 ance of the most complicated, and vital work, of digestion 

 and alimentation. 



The enteric canal, anatomically, is divided, roughly 

 speaking, into mouth, oesophagus (Fig. 112), stomach, 

 and small, and large bowel (Fig. 113), each division being 

 structurally somewhat different, and functionally some- 

 what distinct, from the other, in accordance with the 

 physiological character of its specific contribution to the 

 common work. It is needless to say that every portion 

 of the canal, and so far as yet discovered, every accessory 

 structure, and organ, appertaining to it, is most perfectly 

 adapted for the performance of its individual ofHce, and 

 unitedly, for the complete accomplishment of the great 

 functional work of preparing the raw alimentary materials 

 of our everyday diet, to meet the nutritive requirements 

 of our everyday life and work. Thus, the mouth, with 

 its masticatory, and insalivating, machinery, performs on 



