HISTOLOGY OF THE POSTERIOR PITUITARY. 493 



canal of the cord; finally the particles of carmine may be traced 

 right up to the free end of the canal, where the spinal cord 

 opens into the exterior by the blastopore; therefore it is made 

 manifest that the infundibular duct carries a stream of oxygen- 

 bearing water for the nutrition of the tissues and the carrying 

 off of their effete products." Alluding to personal studies to 

 which we will presently refer, Berkley then adds: "It is quite 

 curious to find essentially the same structures preserved in as 

 high a vertebrate as the dog, and descending to so low a zoolog- 

 ical order as amphioxus, though, as Miiller remarks, the pitui- 

 tary is practically the same from myxine to man" Yet in man 

 the infundibular orifice is closed, and the posterior pituitary, 

 during its evolution, must, therefore, have assumed some func- 

 tion other than that possessed by the organ during the earlier 

 phases of its career and of which the earlier forms should also 

 show traces. 



We have seen that oxygenation of the blood, the highest 

 development of the function carried out by the water-vascular 

 system in the amphioxus, belongs to the domain of the ante- 

 rior pituitary. The remaining inference afforded by the 

 phylogenetic history of the organ, therefore, is that the pro- 

 spective posterior pituitary body is represented in the amphioxus 

 and amoccetes by the group of nerve-cells around and at the ~back 

 of the upper opening, where the duct widens into the ventricular 

 cavity. 



We must state that we consider this perfect concordance 

 between the functions of the anterior and posterior pituitaries 

 as we have conceived them and those found throughout the 

 entire evolutional scale of zoological forms as far back as the 

 amphioxus by Andriezen as very strong evidence that our views 

 are sound. 



THE HISTOLOGY AND PHYSIOLOGY OF THE POSTERIOR 

 PITUITARY BODY. 



What is the physiological relationship between the two 

 lobes? Dejerine 7 states that vertical and horizontal sections 

 of both organs show that they are absolutely distinct and sepa- 



7 D6jerine: "Anatomic des Centres Nerveux," vol. i, 1895. 



