HYPOPHYSIS CEREBRI 315 



hypophysis, but the view has been contested upon many sides. 

 First Hoffmann, and later Orr, assumed a relationship between 

 the hypophysis and the ectoderm of reptiles. As the result of 

 his later investigations (1894), v. Kupffer, who had previously 

 accepted the ectodermal origin of the hypophysis in all verte- 

 brates, arrived at the conclusion that, in addition to the ectoderm, 

 the entoderm the epithelium of the archenteron in particular- 

 is concerned in the formation of this organ. According to him, 

 the hypophysis has three primitive sources of origin ; the first is 

 ectodermal and is a remnant of a phylogenetically old oral cavity 

 (palasostoma), situated above the spot where the mouth afterwards 

 develops, and which, later, becomes Rathke's pouch ; the second, 

 which is entodermal, is situated behind the pharyngeal membrane 

 and is formed by an outgrowth, sometimes hollow and sometimes 

 solid, of the cephalic intestine (preoral intestine), the blind end 

 of which forms the pouch described by Seessel ; the third or 

 cerebral portion is provided by the infundibulum and infundi- 

 bular gland. In the monorhines and myxinoids, the infundi- 

 bular gland only is present, the palasostoma forming the perma- 

 nent nasopharyngeal passage. In Petromyzons, Elasmobranchii, 

 and Teleosteii, the infundibular gland and the dorsal gland-com- 

 plex of the naso-pharyngeal passage are both present. 



v. Kupffer's view is shared by Valenti and partly also by 

 Nussbaum ; but the inclusion of the entoderm in the formation of 

 the hypophysis is denied by St. Remy in the case of birds and 

 mammals, by Hoffmann in the case of Selachians, and by B. 

 Haller in the case of all vertebrates. Valenti, who has carried 

 out a fresh series of investigations with embryo chicks and rab- 

 bits, maintains the view, however, that the hypophysis contains 

 an ecto-entodermal portion, derived from the preoral intestine. 

 Corming and Rossi, on the other hand, insist upon a purely 

 ectodermal origin. 



PHYSIOLOGY OF THE HYPOPHYSIS. 



Experimental Extirpation. It was Horsley (1885) who, in 

 order to compare the results of the removal of the hypophysis 

 with those which follow thyroiclectomy, first undertook the extir- 

 pation of that organ. His experiments, like those of Dastre 

 (1889) and Gley (1891) were completely negative, the animals 

 dying immediately after operation. Following the theory pro- 

 pounded by Marie and Marinesco concerning the pathogenesis 

 of acromegaly, Marinesco (1892) next carried out extirpation 

 experiments with cats. Since that date, hypophysectomy has 

 been performed on animals of different species, and according 

 to various methods. But these attempts, if we except quite the 

 most recent, supplied no satisfactory information concerning the 

 importance of this organ to the life of the organism and the nature 



