Ctt. XXIII.] PITUITARY AND PINEAL GLANDS 34 1 



sentative of the supra-renal, it may be removed without any harm to 

 the animal. The other portion of the Elasmobranch supra-renal is 

 paired, and derived from the sympathetic ganglia. This corresponds 

 to the medulla ; it contains the same chromogen as the medulla of 

 the mammalian supra-renal, and extracts of it have the same physio- 

 logical action (S. Vincent). 



The Pituitary Body. 



This body is a small reddish-grey mass, occupying the sella 

 turcica of the sphenoid bone. It consists of two lobes a small 

 posterior one, and an anterior larger one, somewhat resembling the 

 thyroid in structure. The anterior lobe is developed as a tubular 

 prolongation from the epiblast of the buccal cavity. The growth of 

 intervening tissue soon cuts off all connection with the mouth. The 

 alveoli are approximately spherical ; they are filled with nucleated 

 cells of various sizes and shapes not unlike ganglion cells, collected 

 together into rounded masses, filling the vesicles, and contained in a 

 colloid substance. The vesicles are enclosed by connective-tissue, 

 rich in capillaries. The posterior lobe is developed from the floor of 

 the third ventricle ; it consists mainly of vascular connective tissue, 

 and includes masses of epithelial cells. In the adult it contains no 

 distinct nerve-cells, but it receives nerve-fibres which originate in 

 the grey matter behind the optic chiasma. 



Disease of the pituitary body produces the condition called 

 acromegaly, in which the bones of Rmbs and face hypertrophy. 

 When the gland is removed in animals, tremors and spasms occur 

 like those which take place after removal of the thyroid. Death 

 usually occurs within fourteen days. Some observers have stated 

 that overgrowth of the pituitary occurs after excision of the thyroid. 

 But there is no ground for the assumption that the two glands ha\t 

 a similar function. Acromegaly is a very different disease from 

 myxoedema. The injection of extracts of the organs are also different. 

 Thyroid extract produces a fall of arterial pressure. Extracts of the 

 anterior lobe of the pituitary body are inactive ; but extracts of the 

 posterior lobe or infundibular body contain two active substances, 

 one of which produces a rise, and the other a fall of blood-pressure. 

 A second dose of the former of these injected soon after the first dose 

 is inactive ; and so it is not the same thing as in supra-renal extract. 

 The chemical nature of the two substances is not known. Pituitary 

 extracts when injected into the blood also produce diuresis (Schafer). 



The Pineal Gland. 



This gland, which is a small reddish body, is placed beneath the 

 back part of the corpus callosum, and rests upon the corpora 



