Abstract
Most of the studies in the present work have been done on hand isolated unfixed rabbit medullary neurons. Some studies were also made on neurons from the anterior horns, sympathetic ganglia and dorsal ganglia of rabbits, guinea-pigs and frogs. A total of approximately 7000 cells were examined. (i) The effects on the cell structure of the haematoxylin and eosin staining procedure and mounting in DPX was examined in 30-40 neurons isolated in 0.9% saline. The cytoplasm and nucleolus appeared to be precipitated and shrinkage of the areas of the cell body, the nucleus and the nucleolus occurred down to 21%, 11% and 6. 5% respectively of their original unfixed areas. (ii) In 150-200 isolated rabbit medullary neurons unfixed and fixed the DNA appeared to be in the nucleoplasm but not in the nucleoplasm of cells in tissue sections. It was concluded that in the latter case dehydration before embedding could extract the DNA from the nucleoplasm. The experiments were made with the enzyme DNAse, and with stains. (iii) Rabbit medullary neurons were incubated in '199' medium plus calf serum (14%) and phytohemagglutinin (0.7%) and the incidence of the presence of two nucleoli increased from 17% to 29%. (iv) The neurons from the rabbit Deiters' nucleus were isolated and examined in 0.9% saline by ultra violet microscopy with an exciting wavelength of 3650A. They fluoresced with an apple green colour having a wavelength from 5400-5700A. This auto-fluorescence was concluded to be due to lipofus-cin. (v) A nucleolar interface was detected by light microscopy in all the 1500 nerve cells of the four different kinds from the four different species examined. It was concluded that this interface was a membrane, and this appears to be a new observation.