148 Herring 



Similar bundles of fibres are found in the solid neck of the posterior 

 lobe of the monkey's pituitary. Here, too, the cells of origin lie below, 

 and the fibres run upwards; they must be regarded as ependyma cells 

 which have become enclosed in the body of the organ. 



In the body of the posterior lobe the ependyma and neuroglia fibres 

 make up a very thick network. The presence of true nerve cells in the 

 pituitary is very doubtful. In preparations made by Cox's modification 

 of Golgi's method the cells stained resemble neuroglia cells and are all of 

 the same type. That this is not an accident is shown by the uniformity 

 of the results in different specimens, and by the fact that when the sections 

 include brain substance the true nerve cells in the latter are well and 

 characteristically shown. The neuroglia cells, like those of adjacent parts 

 of the brain, are spider cells with very numerous processes. In Cajal 

 preparations the fibres run through the cell, the body of which is often 

 difficult to distinguish. 



The nerve supply of the glandular portion of the pituitary body is stated 

 by Berkley to be derived from the sympathetic system. Branches enter 

 the gland with the blood-vessels, and end among the epithelial cells. Cajal's 

 method shows fine fibres entering amongst the cells of the epithelial invest- 

 ment, especially in its thicker portions near the neck of the infundibulum. 

 The fibres come from the nervous portion, where they are closely associated 

 with the blood-vessels. I have not been able to trace their origin, but for 

 developmental reasons am inclined to believe that they accompany the 

 blood-vessels into the gland, and are, as Berkley states, derived from the 

 sympathetic system. Neither by Golgi's nor Cajal's method have I been 

 able to find nerve fibres in the anterior lobe, but I have not specially 

 investigated this point. 



The nervous tissue of the posterior lobe of the pituitary appears, then, 

 to have the structure assigned to it by Virchow in 1857, and to be made 

 up of neuroglia and ependyma cells and fibres. There are, however, other 

 very important elements present. The epithelial covering is in contact 

 with the nervous portion from an early stage of development, and grows 

 around it. But the relation becomes still more intimate, for the epithelial 

 cells invade the nervous portion. This ingrowth may take place at any 

 part of the lobe, but, in the cat's pituitary, is most marked in the region 

 of the neck of the infundibulum, and at the posterior reflection of 

 epithelium. In the latter situation the epithelial cells frequently ac- 

 company the blood-vessels for some distance into the lobe. Strands of 

 cells retaining their connection with the epithelial investment are often 

 seen passing into the nervous substance ; at other times cell islets of a 

 similar nature are found at variable distances from the epithelial covering. 

 The islets consist of well-defined epithelial cells, and in preparations fixed 

 in Flemming's solution are vevy distinct. They react to stains in a 

 manner which identifies them with the cells of the epithelial covering. In 

 the adult cat they are often very numerous, especially in the neck of the 



