neurophysiology: an integration 



19-27 



past to modulate the present — all such improved 

 patterns of organization make for the greater capac- 

 ities of the higher mammals over lower forms. 



It is highly doubtful that investigations so far have 

 revealed all the significant patterns of organization 

 that exist in developed nervous systems; nor is it at 

 all certain that the same basic patterns are used 

 throughout the full range of organisms after the 

 pattern has first appeared. Invertebrates control 

 muscle tension by a vastly different neuromuscular 

 mechanism than do vertebrates (Furshpan), and the 

 gamma motor system works quite differently in the 

 frog and in the mammal (Eldred). Nonetheless, there 

 seems no present reason to assume that the continued 

 improvement in performance by the higher mammals, 

 and particularly by the primates and man, is the 

 result of progressive improvement in neural patterns. 

 Rather, just as the reacting elements seem to have 

 reached their asymptote with the arrival of vertebrates 

 and arthropods, so have the patterns perhaps reached 

 their symptote with the arrival of mammals. The 

 remaining freedom for advance is then in the numbers 

 of usable elements and combinations, ratlin than in 

 the kinds. 



quantities. The point has been developed elsewhere 

 (117), that a simple increase in number can bring 

 about new dimensions of quality. The game "Twentv 

 Questions' is utterly trivial when the number allowed 

 is half a dozen, is highly sophisticated when the 

 number is unlimited. Adding more memory banks 

 and programming elements to computers enables 

 them not merely to do more or faster calculations, but 

 also to perform new types of processes. An increased 

 channel capacity in the nervous system permits the 

 handling of more information, of course, but also it 

 permits the more intricate handling of that informa- 

 tion. It seems quite probable thai the liner nuances 

 of human behavior depend primarily on man's 

 greater store of effective neurons (Bremer). Re- 

 versible and irreversible decreases in this store ex- 

 plain many facets of perception, anxiety and 

 psychosis — as will lie developed later. A similar quan- 

 titative view of the defect in some aphasias has been 

 supported by a stuck of word frequency distribution, 

 more and more common words being lost with more 

 neuron destruction (Howes D. H., Ill, & Geschwind, 

 N., personal communication). 



value of the nervous system. Man's value judgment 

 of ranking animals on a behavior scale is supported 

 by a seeming value judgment of the body in cherishing 



its nervous system. This organ is wrapped in multiple 

 membranes; is floated in liquid, the composition of 

 which suggests a purely supportive function (Davson) ; 

 and is encased in bony armor — all giving maximal 

 protection against mechanical damage. Carotid re- 

 ceptors help insure a constant supply of blood of 

 proper composition at the portal of the brain, and 

 the state of the bathing fluid is further under precise 

 regulation from central receptors for osmotic pressure, 

 temperature, carbon dioxide, etc., which supplement 

 the peripheral regulators (Schmidt, Ingram, 

 Ortmann). Local vascular adjustments protect against 

 oxygen excess (Schmidt) or deficit (Kety). In addi- 

 tion, a special permeability barrier exists, so that the 

 intercellular milieu of the neurons is doublv protected 

 from outside perturbations (Tschirgi). Only in the 

 vicinity of the special chemoreceptor areas is the 

 blood-brain barrier breached (Ortmann). More- 

 over, glia cells closer) invent neuron elements and 

 must contribute to the line control of their environ- 

 ment, indeed, there may Ik- essentially no true ex- 

 tracellular space [but sec (Jcrschenfeld rt al. (122)]. 

 Finally, a fifth to a half (Sokoloff) of the resting me- 

 tabolism of the body is allotted to a nervous system 

 i (instituting, even in man, miK .1 fiftieth of iis weight , 

 and this expensive organ is maintained relatively 

 well through a starvation period, all other organs 

 except the heart being used as fuel. The nervous ^\- 

 tern is indeed a well-buffered black box, protected 

 from all inputs save those external and internal ones 

 for which ii is specifically coded. 



Maintenance 



homeostasis and growth. A further topic needing 

 consideration before dealing with the nature, activa- 

 tion and formation of neuron patterns, and the be- 

 havioral consequences of these is the homeostasis of 

 the neural machine. This has already been en- 

 countered in connection with the devices evolved bv 

 higher organisms to protect the nervous system from 

 mechanical insult and chemical vicissitudes. Xow, the 

 existence of a continued protoplasmic flow and the 

 nature of neural metabolism, including its magnitude, 

 substrates and uses, need attention. Later sections 

 will consider the relation of metabolism to trans- 

 mitters and drug action, to proteins and nucleins and 

 information coding, to ions and the maintenance of 

 membrane potential and threshold levels and con- 

 duction, and to the control of rhythmic electrical 

 beats via a trip mechanism. 



The carlv suggestion thai a severed nerve fiber 



