314 



MANUAL OF HISTOLOGY. 



Robin of bipolar cells in the ganglia of fishes. 2. Phil. Transfer the year 1863, vol. 

 eliii. part " P- 543- 3 - In llis excellent treatise (Observationes de retince structura 

 penitori) M. 'Schultze divides ganglion cells into four classes, and, as far as our own 

 observation goes, they may be so classed with propriety, though intermediate forms 

 also exist. The four are as follows : (a) those that have neither neurilemma nor 

 medullary sheath, as in the brain, cord, and retina ; (b) such as have neurilemma, but 



Fig. 305. Multipolar ganglion cells from the human brain. 1, a cell, one of whose 

 processes (a) becomes the axis cylinder of a nerve fibre (&) ; 2, a cell (a) connected 

 with another (b) by means of a commissure (c) ; 3, diagram of three cells (a) con- 

 nected by means of commissures (6), and running into fibres (c) ; 4, a multipolar cell 

 containing black pigment. 



no medullary envelope, as in the sympathetic and other peripheral ganglia with 

 multipolar elements ; (c) ganglion cells with medullary envelope, but no neurilemma, 

 of which we see isolated examples in the N. acusticus ; and, finally, those which 

 possess both medullary sheath and neurilemma, as in the bipolar cells of spinal 

 ganglia. Corresponding to these we have four species of nerve fibres, namely, (a) 

 naked axis cylinders ; (b) axis cylinders with neurilemma, but without a medullary 

 sheath, as in the olfactory nerve and Remalcs fibres ; (c) axis cylinders without a 

 primitive sheath, but supplied with an envelope of medullary substance, as for 

 instance in the white matter of the nervous centres ; and finally, (d) axis cylinders 

 surrounded by both medulla and primitive sheath, the usual form. 4. Strange to 

 say, the existence of commissural fibres between the central ganglion cells is stoutly 

 denied byDeiters. I myself have seen them most certainly many years ago, and believe 

 in them still. 



179- 



Here also, as in the consideration of the nerve tubes, the question 

 arises, Does the description of the ganglion cell just terminated give us 

 its complete structure, or does it possess a finer texture? 



At present the extremely various views on the subject supply us with 



. but very inadequate materials for replying to this query conclusively. 



Thus the nerve fibre, i.e., the axis cylinder, has been stated to spring from 



the nucleus or nucleolus. Among the various observations made on this 



