THE PITUITARY BODY 14S 



and sperm began to develop and could be clearly recognised. The 

 conclusion drawn was that we had demonstrated a connection be- 

 tween the hornionic activity of the gland and the physiological m-ge 

 to migrate. 



The pituitary body of fish is a small body resting just in front 

 of the lobi inferiores and is attached to the ventral walls of the 

 infundibuhim either cUrectly or by a stalk. In the eel it is ovoid 

 in shape, and Mlien divided sagittally in the middle line, it is some- 

 what kidney-shaped, with the hilum facing the infundibulum. 

 The pituitary body in the eel consists of two lobes anterior and 

 posterior ; they are entirely different, both in their structm'e and 

 development. The posterior lobe is developed as a hollow down- 

 growth of the part of the embryonic brain w^hich afterw^ards becomes 

 the third ventricle. In fishes the cells wliich compose its walls 

 become converted into nerve-cells and fibres, and, as the lobus 

 infundibuli, become an integral part of the brain. The anterior 

 lobe is developed as a tubular prolongation from the epiblast of the 

 lining epithelium of the cavity of the mouth, with which it is there- 

 fore originally in connection. In the adult it is constituted of a 

 large number of tubules or alveoli like those of a secreting gland, 

 and in like manner Uned by epithelium. It is very vascular and has 

 a number of sinusoidal spaces. Vesicles are sometimes present, 

 and these may be filled with a colloid substance similar to that 

 found in the thyroid vesicles. 



The posterior lobe of the eel consists of two parts, closely related, 

 the pars intermedia and pars nervosa. In comparison with a 

 mammalian gland, the pars nervosa takes a very small share in 

 the make-up ; a number of nerve fibres spread out fan-like and 

 loose themselves in pockets of the pars intermedia. This consists 

 of a large number of acini, the peripheral part of which is, in the 

 resting stage, composed of tlu-ee or four layers of cells, while in the 

 centre is a circle of ependyma cells connected with the neuroglia 

 of the pars nervosa. In the active stage, that is to say towards the 

 autumn, a very different picture is seen. The peripheral cells are 

 almost entirely replaced by a yellow-staining secretion. In the 

 centre the lumen is surrounded by empty ovoid cells. In some 

 acini the granular secretion is converted into an ovoid refractile 

 mass of brown colloid. 



Surrounding each alveolus is a meshwork of fine capillaries, and 

 witliin them can be clearly seen small masses of brown colloid,, 

 together with a few red blood corpuscles. The blood vessels arise 

 from small peripheral arteries which can be seen passing inwards 

 to end in the capillary anastomosis. 



