DEVELOPMENTAL EVOLUTION 237 



while the posterior is undergoing a metamorphic change, 

 by which the lumen of the canal is being occluded by the 

 deposition of connective tissues, previous to cerebro-spinal 

 excretional discharge, through the line of differentiation, 

 and secured by the highly developed coccygeal glandular 

 receptacle and exit vasculature a mutual approach 

 (see Figs. 30, 32), of the two anterior terminal ends of the 

 neurenteric canal, is taking place ; the buccal cavity and 

 the floor of the mid brain extending themselves towards 

 each other until they have become absolutely contiguous, 

 when their respective tissues cohere, and become conjointly 

 encapsulated, whereby is produced, the structure, or organ, 

 known to anatomists as the pituitary gland (see Fig. 32), a 

 structure which is supposed to be functionless, and which 

 from time to time has had various, somewhat fantastic, 

 duties, assigned to it. These assignments of function it 

 is not now necessary to refute, but it is necessary, that we 

 should claim, for this developmental production, a function 

 of the highest order, that any bodily structure can lay 

 claim to, viz. that of providing an antero-central outlet for 

 the drainage of the great central cerebral organ, the brain. In 

 claiming for it this most important vital duty, we base our 

 opinion on its essential anatomical structure and histo- 

 logical characteristics, which are those of a true gland, its 

 simultaneous, provision and opening, with that of occlusion, 

 of the posterior-inferior end of the neurenteric canal, the 

 provision of structural developmental materials for the 

 establishment of circulatory facilities between the buccal 

 cavity and the cerebral cavity, at the earliest period neces- 

 sary for the regulation of intra-cerebral pressure, the facts, 

 that a cartilaginous, and then an osseous, foundation (see 

 Fig s< 33^ 34 35>36), are produced for its support, and inde- 

 pendent existence, as one of the first acts of solidification, 

 and ossification of the future skeleton, and the absolute 

 necessity, for the preservation of the hygiene of the intra- 

 cranial structures, of an outflow mechanism, capable of 

 meeting the requirements of the central cerebral organs, 

 and inter-meningeal spaces, as these requirements, by the 

 process of developmental necessities, come into existence. 

 During the period of foetal changes and development, 

 great variations are effected in the completeness with 



