Blood-chemistry.—With improved technique, chemical exam ination of the blood for non-protein nitrogen (in kidney disease), sugar and gases, cholesterol, calcium, phosphates, chlorides and bilirubin has become a method of clinical laboratory routine and essential for correct diagnosis and treatment. Much work has been done on the hydrogen ion concentration of the blood and the condi tions of (I) acidosis, or diminution in the alkali reserve of the blood, which occurs in two forms, ketosis, as in diabetes mellitus, and another due to retention of phosphates, as in renal disease, and (2) of alkalosis or alkalaemia in which the alkalinity of the blood is increased, as in forced breathing when carbonic acid gas is removed in unusually large quantities from the lungs. Alkalosis has, like a fall in the calcium salts and the poisonous effect of guanidine, been thought to cause a convulsive state—tetany, which forms part of the condition called spasmophilia seen in children.
Bacteriology (q.v.) has revealed the organism responsible for a number of diseases and so opened the way to specific treatment and the prevention of the infection. In the case of scarlet fever (see INFECTIOUS FEVERS), ascribed to haemolytic streptococci, G. F. and G. H. Dick have elaborated a test (the Dick test), analo gous to the Schick test in diphtheria, whereby those susceptible to the disease can be detected and so artificially protected against it by an antitoxin The recognition of tularaemia (due to a cocco bacillus), a disease of rodents and transmitted to man by the bite of the horse fly, and of melioidosis also a disease of rodents and due to the Bacterium whitmori, in which the exact method of its transmission to man is uncertain, bear on the desirability of the closer correlation of the human with veterinary medicine. Invis ible viruses or ultra-microscopic organisms, also called filter-pass ers (see FILTER-PASSING VIRUSES), because they are so minute that they pass through the fine pores of a Chamberland or other filter, have attracted much attention and many diseases in man and animals are with a fair degree of certainty or probability ascribed to their agency.
Bacteriophage.—D'Herelle described a phenomenon, previ ously noted by Twort in 1915, often known by D'Herelle's name, which he interpreted as the existence of an ultra-microscopic virus which lives as a parasite upon living bacteria and leads to their destruction and solution. The general opinion about the active substance responsible for these changes in bacterial cultures, and called by D'Herelle the microbe bacteriophage, is that it is not an ultra-microscopic virus, but an enzyme or ferment produced by the undoubted bacteria themselves.
Protozoan infections (see PROTOZOA) are the cause of a num ber of diseases, such as yellow fever (Leptospira icteroides), a form of infective jaundice (Spirochaeta icterohaemorrhagica), rat-bite fever (Spirochaeta morsus-muris), and seven-day fever in Japan (Leptospira hebdomadis), and probably sandfly fever (q.v.) (a Leptospira resembling that of yellow fever). Thus their prevention and the employment of curative antitoxins has been rendered possible.
Immunity (q.v.).—After a fever the individual usually becomes immune and protected against another attack; this is acquired im munity; the blood of such a person contains antibodies which an tagonise the cause of that disease, and advantage has been taken of this to inject the blood serum of patients convalescent from measles into persons who have not had the disease so as to render them immune.
Anaphylaxis (q.v.).—The reverse of immunity is hypersensi tiveness (anaphylaxis, allergy) which is shown by idiosyncrasies and forms the underlying factor in asthma and other diseases spoken of as "toxic idiopathies ;" the substances responsible for the symptoms can be detected by skin tests and the appropriate treatment thus employed. Protein shock therapy is also employed for asthma and chronic arthritis. The importance of "focal in fection" such as dental disease (see DENTISTRY), is now much more fully recognized. (See THERAPEUTICS.) Exact studies upon the chemical activities of bacteria now in progress are beginning to throw light on the actions of toxins and the chemical factors involved in immunity reactions.
Radiology (q.v.).—In radiology there has been a steady ad vance in the methods of diagnosis and treatment ; technique has been elaborated and special methods have been introduced. Sub stances opaque to X-rays have been employed in various direc tions ; thus lipiodol has been injected into the bronchial tubes to demonstrate dilatation of their lumen, into the spinal column to show the position of tumours, and even into the uterus to detect pregnancy. The condition of the gall bladder and the presence of gall stones can be made evident by organic compounds of iodine and bromine (tetra-iodo-phenol-phthalein and tetra-brom-phenol phthalein), which after being taken by the mouth are excreted in the bile and show up under X-rays (cholecystography). Injection of air into the peritoneal cavity enables a clearer X-ray picture of the abdominal viscera to be obtained. The skiagrams of the jaws, showing the presence or absence of infection of the apices of the teeth and of the skull, showing the condition of the sella turcica, have facilitated the detection of focal sepsis and of pitui tary disease respectively. The improvement of technique has made advances in treatment possible. By intensive X-ray exposures, following the Erlangen practice, the remedial therapy of deep seated malignant growths has been pursued. The radium treat ment of cancer in positions where the radium (q.v.) can be brought into close contact with the growth, is now carried out with in creasing frequency, and team work in this treatment of cancer of the uterus has been adopted in a number of hospitals. Side by side with advances in treatment the effect of X-rays on the tissue cells has been investigated experimentally; the results have a very definite bearing on the methods and dosage employed in treat ment, for the destructive changes induced in the cells may give rise to grave symptoms and even death. It appears that X-rays and the gamma rays of radium may set up secondary radiations in the tissues and so cause severe changes.