124 Herring 



The pituitary of the monkey more closely resembles that of man, and 

 is a t3'pe in which greater fusion of the original elements from which 

 it is developed has taken place. The posterior lobe is solid throughout. 

 Its investment by the epithelial portion is not so complete as it is in the 

 cat, and only a small cleft remains as the representative of the original 

 buccal pouch. 



The pituitary of the dog offers in some respects a type which is inter- 

 mediate between that of the cat and that of the monkey. The posterior 

 lobe is solid, but the cavity of the third ventricle of the brain is continued 

 downwards and backwards towards the neck of the posterior lobe. The 

 epithelial investment is very complete, and the cleft in it well developed 

 as in the cat. The colloid cysts are more numerous than in the pituitary 

 of the monkey, and their arrangement and structure present features 

 which distinguish them from those of the cat's pituitary. The morphology 

 of the pituitary bodies of the cat, dog, and monkey will be described briefly, 

 and the structure of the various parts more minutely detailed in the cat. 



For the investigation of the finer structure of the pituitary body 

 Flemming's fixative gives the best results; a 10 per cent, solution of 

 formol and saturated corrosive sublimate have also been employed. 

 Sections have been cut serially in a vertical antero-posterior plane ; these 

 show the relations of the various parts of the pituitary to one another 

 better than do sections cut in other directions. Most of the material has 

 been cut in parafiin, but the freezing microtome has also been used, and 

 the Golgi preparations cut by hand. 



The structure of the anterior lobe is shown to the best advantage by 

 staining with eosin and methylene blue, or by the employment of some 

 of the many methods devised for the staining of blood films. Many 

 preparations w^ere made by Cajal's silver reduction method, which is 

 especially valuable for showing the fibrils of the neuroglia, and the 

 ependyma cells of the posterior lobe. Cox's modification of Golgi's 

 method was also adopted for the investigation of the nervous elements. 

 Fresh tissues have been teased out and examined in salt solution and 

 in osmic acid, and chromic acid fixed preparations have been cut by the 

 freezing microtome. The blood-vessels were also injected from the common 

 carotids with carmine gelatine, and the vascular supply of the pituitary 

 body studied in thick sections. 



A word must be said about the removal of the pituitary body for 

 purposes of examination. In order to investigate the question raised by 

 B. Halle r as to the presence of an opening on the median ventral aspect 

 connecting the epithelial cleft with the subdural space bj' means of a 

 lymph space, it is almost essential to remove the sella turcica and part of 

 the brain from below, to decalcify the bone and cut sections of the pituitary 

 in situ. This can be more readily done in the young animal. For most 

 purposes it is sufficient in the adult animal to dissect the bone piecemeal 

 from the dura mater, which forms an envelope to the pituitary, thickened 



