314 INTERNAL SECRETION 



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of the skull, while the other communicates with the epithelium of 

 the oral mucosa. The hypophysis is now a closed structure, but 

 in the human embryo, in the second half of the second month, 

 hollow tubes' are formed in the anterior and ventral wall of the 

 cavity ; these penetrate into the surrounding connective tissue, 

 which is very vascular (embryo rabbit, 30 mm.), and become cut 

 off from the cavity of the hypophysis to form isolated structures. 

 The whole of the pouch now breaks up into tubes in the same 

 way, thereby forming the anterior lobe, in the posterior portion 

 of which traces of the original cavity still remain. The anterior 

 lobe is now joined by means of connective tissue to the posterior 

 lobe, which has in the meantime developed from the infundi- 

 bulum. 



Traces of embryonal development are observed in the human 

 hypophysis during the entire course of post-fcetal life. The 

 fissure lined with epithelium which is present in the anterior 

 lobe, is the post-fcetal representative of the original pouch ; while 

 the cavities filled with colloid, by which this fissure is frequently 

 replaced, are the outcome of the division of the pouch. Erdheim 

 discovered that, from uninvolved remnants of that portion of the 

 hypophysis cavity which is inserted in the anterior lobe, 

 agglomerations of pavement epithelium are formed; these are 

 encountered within a circumscribed area of the anterior lobe, 

 either in isolated groups or associated with adelomorphous cells 

 or vesicles. According to Erdheim, these agglomerations of 

 pavement epithelium may develop into pituitary tumours of the 

 kind known as pavement epithelium sarcoma. 



The road traversed by the hypophysis in the course of its 

 development is represented', in all except a few isolated instances, 

 by a bony channel which passes through the sphenoid bone and is 

 called the canalis cranio-pharyngeus. In and under the mucosa 

 of the pharyngeal roof of new-born infants, Erdheim discovered 

 a cord composed of hypophysis tissue which he named the 

 ' pharyngeal roof hypophysis " (Rachendachhypophyse). Haber- 

 feld, who carried Erdheim's investigations still further, found 

 that this cord, which he termed " hypophysis pharyngea," was 

 constant in man at all ages; he did not regard this structure 

 as an embryonal remnant, but believed it to be a fully developed 

 accessory hypophysis, with a function identical with that of 

 the true hypophysis. Haberfeld showed that, in isolated cases, 

 remnants of hypophysis tissue visible to the naked eye are 

 situated along the entire length of this cord, and that they may 

 form the site of origin of hypophysal tumours. As a matter of 

 fact, Erdheim observed such a tumour in an unusual situation, 

 the course of its development extending below the sella turcica, 

 while the hypophysis, which was normal in size and shape, 

 retained its position undisturbed. 



These findings point to a purely ectodermal origin of the 



