20 



CON ARIC- HYPOPHYSIAL TRACT. 



plexus, but the branches retain a cavity : they are connected 

 by a narrow stalk with the interior of the raid brain. In the 

 section of the brain of an embryo Rabbit 4 centimetres in 

 length, Mihalkovics shows the pineal body projecting behind 

 and above the level of the prosencephalon, and its continua- 

 tion with the pituitary and infundibular tracts, through the 

 intervention of such modified intermediate portions of the 

 deutostomal tract*. 



And here I am inclined to suggest that some cerebral 

 malformations may be viewed in relation to the foregoing 

 transitory evolutional characters. 



Malformations from arrested development, included by 

 Geoffrey St.-Hilaire in the ' Memoires de I'Acad. des Sciences/ 

 and summed up in the ' Philosophic Anatomique,' exemplify 

 phenomena which relate to the space between the fore and 

 hind brains, and which, at such early stages, seem to be 

 associated with the abortive attempt of the alimentary canal 

 to penetrate and traverse such interspace. 



In one of the instances given by Prof. Cleland in his 

 interesting " Contribution to the Study of Spina bifida, Ence- 

 phalocele, and Anence/phalus" \ , occurs the following: — "The 

 cerebellmii is barely recognizable in two lateral parts sundered 

 one from the other." " Projecting forward in the middle line 

 is a hollow pouch about 2 inches long and j inch broad, 

 wdth tolerably tenacious walls, like the finger of a glove. 

 This is the infundibulum and lamina cinerea, and possibly 

 includes the cerebral part of the pituitary body " (or what 

 would have become such if the transcerebral " pouch had 

 not been arrested). " At the tip of this pouch, in front, one 

 can recognize stretched remains of the optic nerves and some 

 slight vestige of the optic commissure." " On raising the 



* ' Entwickelungsgeschichte d. Gehirns,' 1877. 



t ' Journal of Anatomy and Physiology,' vol. for 1882, pp. 262, 204. 



