THE PHYSIOLOGICAL CHEMISTRY OF THE NEURON. 559 



structures are supplied by a vascular net-work similar to that 

 of other cellular structures is shown by the observations of 

 Apathy, who took them for nerve-fibrils. Barker, referring 

 to this feature of his investigations, says: "As to the relations 

 of the neuro-fibrils to sensory surfaces, on the one hand, and 

 muscular tissue, on the other, Apathy makes very definite 

 statements, especially in the last chapter of his article. A 

 neuro-fibril entering the cytoplasm of an epithelial cell of a 

 sensory surface in the leech breaks up (very much as in a 

 ganglion-cell) into a finer reticulum composed of the elementary 

 fibrils. A large number of the constituent fibrils, however, 

 perhaps the majority, leave the cell in order to take part in 

 the formation of a complicated interepithelial fibril-plexus." 

 Neuron and nerve, therefore, appear to be similar to other 

 organs as functional entities and to be subject to the same 

 laws. Still, we can only state that analogy suggests that a neu- 

 ron, its dendrites and nerve, in elaborating lecithin, may depend 

 for their functional activity upon a nuclein rich in phosphorus 

 found in the protoplasm of which their frame-work is formed 

 and in the protoplasmic nuclei; . for, as we will see later on, 

 another source of lecithin exists. 



The role of the blood-plasma is so clearly defined in the 

 foregoing analysis that we deem it permissible to conclude that 

 all the component parts of a neuron cell-body, dendrites, axon, 

 and axis-cylinder serve as channels for blood-plasma. 



Are dendrites provided, as are the cell-body and the axis- 

 c} r linder, with myelin? We have seen that, as stated by Barker, 

 "the stainable substance of Nissl in healthy animals of the 

 same age and species, with the same method of fixing and 

 staining, is tolerably constant in appearance and arrangement 

 in the cell-bodies and dendrites of the same group of nerve-cells." 

 He also states that "the axons appear to be entirely devoid of 

 the stainable substance of Nissl"; but Berkley, 48 referring to 

 the nerve-fiber terminals which are extensions of the axon, 

 writes: "The researches of Flechsig, as well as my own, have 

 shown that these fine branches are furnished with a thin layer 

 of myelin nearly to their termination." As this refers to intra- 



48 Berkley: Johns Hopkins Hospital Reports, vol. vi, p. 89, 1897. 



