198 HELEN L. M. PIXELL-GOODRICH. 



senescent or not. If the nerve-cells are found to be in 

 sufficiently good condition to rule out the possibility of 

 senescence, it is then worth while to spend some weeks on the 

 complete investigation of the bacteria of the bee, on the 

 chance of finding organisms which are possibly pathogenic. 



Attempts were made to do away with the necessity of 

 fixation at all and to examine the nerve-cells in a fresh state. 

 For this purpose the abdominal as well as the cerebral 

 ganglia were investigated. Injection with methylene-blu& 

 has not proved successful with bees (I cannot find any 

 instances in which it has succeeded with adult insects). It 

 must be remembered that the ganglia are surrounded with a 

 considerable tliickness of connective-tissue, and in addition a 

 close net-work of tracheae makes their opacity very great. 



The abdominal ganglia were sometimes rapidly removed 

 from a bee opened under Ringer's solution (Locke's modifica- 

 tion) as usual and then flooded with a dilute solution of 

 methylene-blue in the same solution (•001 per cent.), but 

 penetration was always difficult, and the cells could only be- 

 made clear after a considerable amount of teasing of the 

 ganglionic tissue. Consequently these processes had to b& 

 abandoned in favour of a constant method of. fixation as 

 described above. 



ExEEEIMENTAL RESULTS. 



In the serial transverse sections cells of several different 

 sizes are to be found (11, 18). The cells that I have studied 

 are the large ones with a considerable amount of cytoplasm, 

 when young, and a nucleus measuring 8 by 10 microns or 

 more. No definite Nissl bodies are to be s^n after the fixa- 

 tion used, but some of the older cells are hyperchromatic,. 

 having a varying number of irregular masses of dfeeply- 

 staining substance in the cytoplasm (PI. 11, fig. 8). These- 

 large cells are found chiefly in the following four main 

 regions : 



(1) Almost at the centre of the brain is a wedge-shaped 

 mass of cells pointing towards the anterior surface and 



