152 Herring 



rorni a scaffolding for the posterior lobe of the pituitary, upon which is 

 built up a covering of epithelial cells.^ The relations of the two structures 

 Ijeconie very intimate ; their blood supply is derived from arteries which 

 enter the nervous substance posteriorly ; the veins begin immediately below 

 the epithelium, and return through the nervous substance. Interchange 

 of material between blood-vessels and cells must be through the medium 

 of lympli, seeing that most of the epithelial investment is extra- vascular. 

 Cells from the investing layer grow into the nervous framework, giving 

 rise to epithelial columns and cell islets. Secretion goes on either by an 

 emptjang of material from the cells into the lymph, or possibly by a 

 breaking down and destruction of the wliole cell. The latter indeed is 





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Fig. 15. — Section of part of neck of ])osterior lobe of the pituitary body of an adult cat. 

 From specimen fixed in Fleraming's solution and stained with eosin and methjdene blue. 

 Shows colloid materia,l lying among ependyma fibres and in the central cavity of the neck. 



a, ependyma cells lining central cavity; b, cnlloid material in central cavity; c, ependyma fibres; 

 d, colloid material; e, granular body lying among ependyma filires. 



the more probable fate of isolated epithelial cells, and seems to occur at 

 times in the epithelial investment itself. The material known as colloid 

 substance, which has been supposed by many to be identical with the 

 colloid of the thyroid gland, occurs in comparatively large amounts in the 

 pituitary of the cat, an animal which cannot long survive thyroid extirpa- 

 tion. Further chemical and experimental research is necessary to prove 



' In the posterior lobe of a Belgian hare, a ganglion with large ganglion cells and 

 medullated fibres was found. Tiie ganglion occupied a large portion of one side of the 

 posterior part of the lobe, and the fibres appeared as though entering it obliquely from the 

 side and not through the neck of the lobe. Red bone marrow was also present, and the 

 ganglion may have been part of one of the Gasserian ganglia, which, in the rabbit, are very 

 clo.se to the pituitary body. A large part of the nervous portion of the lobe was destroyed 

 by it. The intermediate portion was large in amount, and its cells thickly massed around 

 the neck. The animal was a healthy adult. 



