A British Medical Association Lecture ON MINOR ENDOCRINE DISTURBANCES: AND THEIR METABOLIC AND PSYCHICAL EFFECTS
Authors: W. L. Brown
Journal: BMJ (1923)

THE last decade of the nineteenth century added greatly to ouir knowledge of the phvsiology of the ductless glanids, while in 1902 Bayliss and Starling's discovery of secretin opened out the vista of a chemical control of the body, in which the nervous system merely acted as a trigger, firing off a series of reactions.This conception was elaborated until it bade fair to dethrone the nervous system from its supreme position, although Langley had already provided the antidote by his generalization that the action of adrenaline on any part was the same as that obtained by stimulating the sympathetic.But the far-reaching significance of that generalization was not yet appreciated." The key to evolution lies in the continuous development of the 'nervous system," said Gaskell.Or, as Elliot Smith put it: "Man has developed and become the greatest of the primates because of his faithful dependence upon the de- velopment of the brain."Considering the struggle the central nervous system has had to obtain control, it is not likely that it would abdicate its suzerainty in favour of the more ancient dynasty of chemotropism.We ordinarily think of the evolution of the nervous system as peacefully accomplished.A struggle for supremacy between two animals or between two species we recognize.But it would appear that a similar struggle accompanies the integration of the multicellular ifidividual.Many apparently peaceful events in nature prove on closer analysis to involve a concealed struggle.Man is a gre- garious animal, but he has not found it an easy task to adjust the desires of the individual to the needs of the community.Philosophers may lament this, theologians may attribute it to original sin, but it should lead the biologist to inquire whether the cells of which he is composed have always found it easy to sink their individuality in that of the organism.The thesis of a hostile symbiosis between the tissues of the body has been skilfully upheld by Morley- Roberts.A strong central government is needed to keep order, and no high degree of differentiation is possible in the animal body without the control of a centralized niervous system, which has gradually acquired an increasing predominance.It is not too much to say that this control, though for the benefit of the body as a whole, may be resented by the individual tissues.Wilfred Trotter de- veloped the argument of a hostility between nervous and somatic tissues, which is expressed in the way the former insulates itself.Without defensive mechanisms no animal can survive in the struggle for existence, and no method of defence remains impenetrable, for, if it were, the species possessing it wouild multiply to the exclusion of others.As evolution proceeds the apparatus for defence comes under the control of a central nervous system.Some defenwive mechanisms, such as nettle cells, never become so controlled, but are replaced by other methods as the nervous system evolves.Certain primitive motor apparatus, such as cilia, also never come under such control, though they persist even in the hiighest animals.In general terms, a central nervous system enables very rapid reactions to occur, and the n-eed for suCh rapidity of response will first be experienced in the struggle for existence, when its advantage is at manifest.G. H. Parker, in his book The Elementary Nervous Sy'stem, has brought new observations inito lationiship with previously known facts, and has impressed upon us atresh that a nervous system starts as a series of I independent receptors and effectors in the deeper layers of the skin, the cells of whiclh sink in deeper and deeper, until they become concentrated inito a central nervous system.Between the receptor and effector an adjustor mechanism develops, which is the germ of the whole associative appa- ratus.