STRUCTURE OF THE MUSHROOM BODIES 



235 



of the anterior and the inner roots above mentioned. " Here it branches, one 

 branch continuing straight on to the end of the anterior root, while the other 

 passes to the end of the inner root. Throughout its whole course the fibre and 

 its two branches are very fine. Nearly the whole stalk and nearly the whole 

 of each root is made up of these straight, parallel fibres coming from the cells 

 within the cup of the mushroom bodies. What other fibres there are enter 

 these bodies from the side, and branch between the straight fibres very much as 

 the deudrites of the cells of Purkinje branch among the parallel fine fibres from 

 the cells of the granular layer in the mammalian cerebellum. These fibres are 

 of the* nature of association fibres." 



Viallanes showed that from the olfactory or antennal lobes, as well as from 

 the optic ganglia, there are tracts of fibres which finally enter the cups of the 

 mushroom bodies, and Kenyon has confirmed this observation. Kenyon has 

 also, by the Golgi method, detected another tract, before unknown, "passing 

 down the hinder side of the brain, from the cups to the region above the oesoph- 

 agus, where it bends forward and comes in contact with fibres from the ventral 

 cord, which exists, although Binet was unable to discover any growth of fibres 

 connecting the cord with the brain. 



"The fibres entering the cups from the antennal lobe, the optic ganglia, and 

 the ventral region, spread out and branch among the arborescent endings of 



COlf; 



po. I 



a. I 



FIG. 252. Section IT, showing the central body (centr.l)} and mushroom body, optic and 

 antennal lobes (a. 1), and procerebral lobes (pc. T) ; <>'. <<!/, outer division of the calyx ; op. n, optic 

 nerve; trab, trabeculum ; fr. n, transverse nerve. 



the mushroom-body cells. The fibres branching among the parallel fibres of 

 the roots and the stalk lead off to lower parts of the brain, connecting with 

 efferent or motor-fibres, or with secondary association fibres, that in their turn 

 make such connections. This portion of the circuit has not been perfectly made 

 out, though there seems to be sufficient data to warrant the assumption just 

 made. 



"Such fibres existing as described, there is then a complete circuit for sensory 

 stimuli from the various parts of the body to the cells of the mushroom bodies. 

 The dendritic or arborescent branches of these cells take them up and pass them 

 on out along the parallel fibres or neurites in the roots of the mushroom bodies 

 as motor or other efferent impulses. 



"This, however, is not all. For there are numerous fibres evident in my 

 preparations, the full courses of which I have not been thus far able to deter- 

 mine, but which are so situated as to warrant the inference that they may act as 



