PHYSIOLOGY Hormones.—Bier found reason to believe that a chemical stimulus (hormone) secreted by the retina initiates the formation of the lens in the larva of the newt (Molge), and that a hormone formed from bone-marrow underlies repair of bone. From this he argued that repair in general is dependent upon special hor mones formed at the seat of the injury according to the type of tissue needing repair.
A large amount of work has been done upon shock and allied conditions: Shock is of great complexity but sudden removal of large quantities of fluid (blood) with the resulting disturbance of the circulation is a fer tile cause. (See SHOCK AND COLLAPSE.) In correspondence with this, treatment by transfusion (see BLOOD TRANSFUSION) is of the greatest value and the methods of transfusion as well as the sub stances to be used were made the subject of numerous enquiries. Broadly speaking, for surgical shock and loss of blood by haem orrhage, injection of solutions of gum arabic are of great value, particularly if a small amount of glucose be added. Volume of injected fluid and rapidity of action are fundamental considera tions, composition of the injected fluid is a matter upon which some latitude can be allowed, and use of blood is by no means obligatory. On the other hand, where transfusion is performed for anaemia (q.v.) due to disease, the character of the injected fluid is of first importance. Here, use of human blood is indicated and it is necessary, by careful examination of patient's blood and donor's blood, to ensure that they belong to blood groups not mutually antagonistic.
Physiological research of unusual importance was carried out (Sherrington, Magnus and others) upon muscle tone in the decerebrated animal by means of which tendon and other reflexes received a clearer explanation and information was afforded upon many reflex postural responses to stimuli that appear to be voluntary. This line of research supplements ex perimental psychology, a branch of investigation that has made strides during the past two decades (see PSYCHOLOGY).
the province of respiration, the relation of lactic acid and muscular exercise to the respiratory quotient has been investigated. Under exercise a lactic acid maximum of 0.3%
in the muscles can be reached in about 3o sec., and this, or rather less, is the longest time that maximal exertions can be kept up. For these short maximal efforts there is reason to believe that carbohydrate alone is used by the muscles. Regulation of rhyth mic respiration, from experiments carried out on cats, appears to depend upon the action of an inspiratory mechanism, the apneustic centre, at the level of the striae acusticae, an expiratory mechanism just below it, both of these centres being controlled by the pneumotaxic centre which is situated in the upper half of the pons. The actual stimulating agent is carbon dioxide.
Very many subjects of enquiry must be passed over here, e.g., discovery of rhythmic contractions of capillaries discovered by a special modification of the microscope; the behaviour of the spleen in poisoning by carbon monoxide ; the action of lead upon red blood corpuscles; researches on bilirubin and urobilin and other pigments in relation to jaundice ; on "buf fering" of blood whereby the addition of a given amount of acid to blood is represented by a smaller change in reaction than would occur in simple watery solutions because of the existence of weak basic salts of carbonic and phosphoric acid, especially in the red corpuscles ; and numerous investigations upon the action of insu lin upon blood sugar and other constituents of the body as well as upon the interaction of insulin and other endocrine secretions.
Energy Expenditure. Of more general interest is a research carried out upon the energy expenditure in sewing with a machine and hemming by hand. Careful measurements were made by means of the respiration calorimeter, but one most instructive result is that influenza exerts a depressant influence on energy output during rest when the patient has apparently recovered completely. In the case of the woman made the subject of meas urement for five weeks after her apparent complete recovery, with the body weight returned to normal, energy expenditure was 4% lower than before the illness.