The Pigmentary Effector System. VI. The Dual Character ofEndocrine Co-ordination in Amphibian Colour Change. In foregoing contributions to this series an attempt has been made to analyse the process of co-ordination in a characteristic mode of behaviour encountered in Amphibia and Reptiles. It is now clearly established that the pituitary gland is an essential agency in determining Amphibian colour change. Accept ing this conclusion, it is still possible to entertain the hypothesis that the secretion of the pituitary gland is merely a condition of the response of the melanophores to nervous impulses in efferent fibres supplying the skin. The present investigation is an attempt to subject this possibility to more rigorous examination. The direct innervation of Amphibian melanophores has not been established by histological examination, and the time relations of pig mentary effector activity in Amphibia do not suggest the intervention of a peripheral nervous mechanism. As shown in the last communication of this series, the melanophores of Reptiles are directly innervated. Experiments on on May 11, 2018 http://rspb.royalsocietypublishing.org/ Downloaded from Pigmentary Effector System. 11 stimulation and section of peripheral nerve trunks have led investigators on Amphibian colour change to ambiguous results, which have been extensively criticised elsewhere. The chief source of misunderstanding arises from the fact that peripheral nerves in general contain vasomotor components. In work on the chameleon it has been possible to demonstrate segmental effects of nervous origin, by employing as a stimulus to generalised pallor an agency for which the receptor surface is localised. For further analysis of co-ordination in Amphibian colour change it now becomes necessary to undertake a more precise definition of the receptive field. A visual response naturally suggests itself as the most convenient type for this purpose. In the European frog (Rana temporaria) various factors, including humidity and temperature, significantly co-operate with illumination to determine pigmentary effector activity. The South African clawed toad is an aquatic Anuran whose chromatic responses are almost entirely determined by photic stimuli. This circumstance has made it possible to explore the problem of co-ordination more thoroughly than in previous researches recorded in this series of communications.In Xenopus as in other Anura there are three types of pigmentary effector organs. These are (a) the epidermal melanophores, (b) the dermal melano phores, and (c) the xantholeucophores. The dermal melanophores are the most important agents in the visible reaction. Their condition can easily be followed by microscopic examination of the web. In what ensues attention is directed to the dermal melanophores, unless otherwise stated.Those who have studied pigmentary effector activity in the English common frog are agreed that humidity and temperature are eminently significant external agencies. In consequence the influence of light assumes a sub ordi...

Co-ordinationthe Integration of Vital Activities VII. Endocrine Coordination 118 VIII. The Mechanism of Nervous Conduction and Excitation. 134 XI.

Recent research on the Rh antigen discovered by Landsteiner and Wiener (1940) has provided conclusive evidence pointing to the occurrence of maternal iso-immunization-i.e. the production of antibodies by the mother in response to the presence of corpuscular antigens in the foetus. Maternal iso-imlunization throws new light on the occurrence of neonatal haemolytic anaemias, of stillbirths, and of abortions in sibships containing members so affected. The importance of its contribution to neonatal and foetal death naturally prompts us to ask to what extent: (a) other foetal antigens evoke the production of maternal antibodies; (b) other maternal antibodies may penetrate the placental barrier with lethal or semi-lethal consequences to the foetus or newly born. These issues had in fact provoked attention before work on the Rhesus antigen clarified current views. Diamond, Blackfan, and Baty (1932) and independently Parsons, Hawksley, and Gittins (1933) suggested that hydrops foetalis, icterus gravis neonatorum, and anaemia of the newborn are different manifestations of the same disease, which they called erythroblastosis foetalis. As the name suggests, its characteristic feature is excess of immature red blood cells in the blood of the foetus. The reason for this remained unexplained until 1940. In 1939 Levine and Stetson described an unusual case of intra-group agglutination in which a woman just delivered of a macerated stillborn foetus was transfused with blood from her husband of the same iso-agglutinogen group (0). Shortly after this she showed all symptoms of incompatible transfusion. Other tests subsequently proved that her serum agglutinated her husband's cells, though she was later transfused with blood from donors of group 0 whose cells did not agglutinate in this way. Tests on a number of group 0 donors, to find a miscible blood, showed that only 20 % were indeed compatible. Levine and Stetson made further tests, and showed that such agglutination was due to an irregular isoagglutinin independent of the factors M, N, or P, but were unable to obtain a

We prepare an extract from a particular tissue suspected as the seat of production or storage of an active component, we also make extracts (E1, E2, E3, etc.) of a wide range of other tissues by exactly the same method. We successively introduce in exactly the same way equal quantities of T and of E1, E2, etc. into the circulation with equally spaced intervals of recovery in an order which excludes masking an authentic or disclosing 163 by copyright.

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