310 INTERNAL SECRETION 



Pisenti and Viola, as well as Caselli, found cells with large 

 nuclei in this layer of the hypophysis, which might be regarded 

 as residues of the endodermal portion of the embryonal hypo- 

 physis (v. Kupffer). According to Launois and Mulon and to 

 Thaon, changes also take place during pregnancy in the posterior 

 portion of the anterior lobe, which these authors interpret as signs 

 of glandular hyperplasia and hypersecretion. 



The communication between the posterior lobe of the hypo- 

 physis and the brain, represented by the infundibulum, varies in 

 man both in length and thickness ; it is composed of glia fibres 

 with few nuclei and the upper portion encloses a canal, the re- 

 cessus infundibuli, which is lined with ependyma cells and repre- 

 sents the continuation of the third ventricle. This hollow is 

 occasionally prolonged into the hypophysis and in some species, 

 notably cats, it constantly extends as far as the posterior lobe. 



The posterior lobe of the hypophysis, the pars nervosa, is 

 considerably smaller than the anterior lobe; it lies posteriorly, in 

 the hollow formed by the glandular portion, the opening of which 

 is downwards. This lobe extends into the sella turcica, in the 

 posterior wall of which a groove for its reception is sometimes 

 observed. Histologically, the posterior portion consists of a loose 

 stroma, which is a mixture of connective tissue elements and 

 neuroglia, the latter predominating. In preparations coloured by 

 Weigert's glia method, Thaon observed a small proportion of 

 fine collagenic fibres, together with a manifold but not close 

 network of glia fibres, in which isolated light, round nuclei were 

 distributed. The tissue had few blood-vessels, and frequently 

 appeared to be infiltrated with an amorphous substance, which re- 

 sembled the substantia gelatinosa Rolandi of the spinal cord. 



The question as to whether the nervous portion of the hypo- 

 physis contains nerve cells has formed the subject of repeated 

 investigation. Both Krause and Berkley describe true nerve cells 

 and nerve fibres ; Ramon y Cajal found cells of an undefined 

 kind in young rats, together with delicate fibres which were cer- 

 tainly nervous and which proceeded from nerve cells situated at 

 the base of the brain behind the chiasma; these nerve fibres 

 descended through the infundibulum, formed a plexus in the 

 posterior lobe and terminated in free branches. Kolliker, as well 

 as Caselli, did not believe that true nerve cells were present in 

 the posterior lobe; they considered the cell elements present in 

 it to be glia cells and ependyma cells. Gentes discovered a 

 considerable network of nrve fibres by Golgi's method, and this 

 finding was confirmed by Thaon. 



According to A. Kohn, the foundation tissue of the neuro- 

 hypophysis is to be regarded as primitive glia in this sense, that 

 its elements are invariably associated with the ependyma, the 

 matrix of all glia elements. He points to the occurrence of a 

 peculiar pigment, which is found chiefly in the glia fibres and 



