332 BIOLOGICAL PHYSICS 



some extent, affording an index of the rate of nerve cell 

 secretion, and nerve fibre growth. Should this estimate 

 be even approximately correct, we at once see that the 

 rate of nerve cell secretion, must be relatively, a great 

 one, and, therefore, that the denied function of nerve cell 

 excretion must be one of corresponding proportions and 

 dimensions, and, in fact, one of the largest, and most 

 omnipresent, of all the excretions of the body. 



The skin, or cutaneous covering, of the whole body, 

 with the mucous, and serous, linings of the various 

 passages, and cavities, large, and small, occurring within 

 the body, represent, respectively, the areas of distribution, 

 of the systemic afferent, or sensory, and the sympathetico- 

 systemic nerve terminals, the muscular structures, striped, 

 and unstriped, representing, in like manner, the respective 

 areas of distribution, of the systemic motor, and the 

 sympathetic, nerve terminals. Each of these terminals, 

 has a form, and method, of terminal distribution, of its 

 own, determined by the anatomical structure, and nervine 

 requirements, of the tissue to which it is distributed, 

 generally known by the name of arborisation, each of these 

 arborisations being, the terminal expansion of a nerve 

 fibril, and known by various names, according to the 

 particular, form, shape, or manner, of its termination. 



Each of these arborisations, or terminal expansions, 

 moreover, represents the process, and manner, of exuda- 

 tion, or excretion, of the plastic component parts of a 

 nerve fibril, and constitutes the final act of growth, of the 

 individual nerve fibril, and its originating nerve cell- 

 death, and disintegration, of the detaching material follow- 

 ing, as soon as its vital connection, or attachment, ceases. 

 Thus, the processes of life and death, follow each other, 

 in the experience of every scale shed, and every organised 

 particle released, from the sensory nerve organism, the 

 vital connection, however, being still for a while main- 

 tained, when the motor terminal fibrils shed their contents, 

 into the sarcous discs of the muscular tissues. 



In the process of shedding, as seen in the breaking down 

 of the sensory nerve terminal expansions, and the filling 

 up of the voluntary muscle fibre discs, and unstriped 

 muscle cells, by the motor nerve terminal expansions, we 



