1. The course of elimination of passive immunity in rabbits injected intravenously with diphtheria antitoxin obtained from a horse, consists of three phases:

(a) an initial loss of 50 per cent, occurring within the first 24 hours;

(6) a gradual constant percentage loss of approximately 25 per cent, from day to day, lasting 6–7 days;

(c) a rapidly accelerated loss of 50 per cent, or more per day after the seventh or eighth day.

2. In rabbits sensitised with small doses of horse serum the same three phases are seen, but

(a) while the initial loss remains the same

(b) the gradual constant percentage loss is of the same magnitude, but lasts only two or three days;

(c) the rapidly accelerated loss occurs after the third or fourth day and over 90 per cent, of the antitoxin present is lost within 24 hours.

3. Possible explanations of the three phases are:

(a) initial loss due either to precipitin to horse serum normally present in rabbits or to saturation of or adsorption to the tissues;

(b) a phase independent of precipitin action;

(c) accelerated loss due to formation of precipitin commencing seven or eight days after injection of horse serum in normal rabbits and three or four days after injection in sensitised rabbits.

While research on the immediate cause of cancer is being pursued with tireless zeal by many earnest investigators it seems that there is still some work to be done on the nature of what may be termed the secondary or accessory causes, those external or envioronmental factors or conditions which predispose to, or favour the onset of the disease in the presence of the determining cause, whether this be chronic irritation of some kind superadded to an inborn tendency and special suceptibility in the patient or the activity of some micro-organism.

1. The results are recorded of the degrees to which standard agglutinable cultures of five serological types Flexner-group bacilli (V, W, X, Y, Z) are agglutinated by non-dysenteric human sera.

2. Certian of these cultures are more highly agglutinated by some normal human sera than was anticipated.

3. In order that the sera of non-dysenteric subjects may all (or parctically all) be found to contain less than 10 or less than 20 units in males and females respectively, the reduction-factors of agglutinability at persent in use for certain of these cultures must be somewhat increased.

4. The conception of a limit, above which no “normal” serum will be found to react, is only valid as a compromise between truth and convenience. Repetition of agglutination-tests capable of measuring the fluctuation of agglutinins in active infection is the only safe and scientific procedure.

From consideration of the above evidence the following conclusions may be drawn:

(1) The prevalence of diphtheria-like bacilli in the fauces of scarlet fever patients on admission to hospital does not definitely follow that of diphtheria outside either in seasonal or yearly prevalence.

(2) The majority of such patients show no clinical evidence of the added infection. It is believed that they are instances of scarlet fever developing in diphtheria carriers, and the presence of the organism does not affect the prognosis. However, cases which present such clinical evidence as a mem branous angina are to be considered as instances’ of true double infection and in them the prognosis is bad.

(3) Bacteriological examination of a series of cases belonging to the former group reveals the presence of true virulent diphtheria bacilli in about 36 per cent., and these organisms may persist in a virulent state for a considerable period.

(4) Routine bacteriological examination to find these cases and their sub sequent isolation materially reduces the incidence of post-scarlatinal diphtheria.

The author was recently asked to advise the Boards of two Dublin hospitals as regards the cleanliness and general suitability of the milk supplied to them. In order to find out exactly the present position of the milk supply, it was decided to investigate bacteriologically the influence of the various factors at work from the time the milk left the cows till its delivery at the hospitals.

In connexion with our inverstigations upon the methods of casuation of food Poisoning outbreaks we considered it advisable to examine a further series of rats.

(1) The inhibiting phenomenon of Neisser and Wechsberg, as frequently observed with bacteriolytic sera, can also be shown to occur with haemolytic sera.

(2) This phenomenon develops early during immunisation, when it is very marked; but as immunisation proceeds it tends to disappear.

(3) In sera examined some time after their removal the inhibiting faculty is seen to disappear first, before any marked change is noticed in its bactericidal titre. This can be shown to occur in vivo also.

(4) The inhibiting faculty is observed only with inactivated sera; fresh and active sera showing complete bactericidal activity at all times. The effects are not however due to complementoids produced by inactivation.

(5) The phenomenon is not due to the action of any of the known anti bodies, or special “inhibiting antibodies”; but it is due probably to dis sociation of the antigen-amboceptor complex. Such dissociation only occurs when amboceptors are present in excess. This explains why inhibition occurs only with high doses of an immune serum.

The serum to be used should be without an antiseptic. Commercially prepared antisera usually contain a small amount of it. It is shown that corpuscles sensitised in them undergo haemolysis without the addition of complement (see p. 427).

(6) Since it is known that the union of antigen and amboceptor is not always a firm one, it is suggested that during early days of immunisation amboceptors of a weak combining affinity are produced. These are replaced later by those which are capable of a more permanent union with them (antigens).

(7) The name “complement-blocking” is not an appropriate one, as com plement could be shown to exist free in the inhibiting fluids. It should rather be spoken of as an “amboceptor-dissociation” effect.

(8) Inhibition is specific. An attempt was made to utilise this fact in differ entiation of strains of true cholera but it was found to have no definite diagnostic value.

The writer wishes to express his indebtedness to Prof. Hewlett for sug gesting the problem to him and also for his kind guidance and encouragement during the course of the experiments. His thanks are also due to Dr Taylor for his valuable assistance.

1. Pneumonic Plague epidemics arise as a secondary manifestation of Bubonic Plague.

2. The prevalence of purely septicaemic cases towards the end of the epidemic is significant as a probable explanation of its decline and termination.

3. Subacute or chronic plague may exist among tarabagans (Arctomys bobac) in Mongolia and Siberia, giving rise to periodical outbreaks of bubonic plague in man, as a result of direct infection from injury due to skinning by trappers or marmot eaters.

4. The tarabagan is easily susceptible to pneumonic plague produced by inhalation of B. pestis in spray form.

5. The existence of Pneumonic Plague carriers has been proved in the 1921 Manchurian epidemic.

6. Rooms where patients have died of pneumonic Plague are not particularly dangerous. In all four instances recorded, sick patients travelling in railway carriages have not infected their fellow passengers.

7. Disinfectants and antiseptics, even in strengths above those usually employed, have very little effect upon plague sputum. Alcohol is the surest means of sterilising the hands and gloves in plague work.

8. We have cultivated B. pestis from seemingly dry sputum of partients.

9. The mask is the principal means of personal protection against Pneumonic Plague.

10. The problem of successful vaccination against Pneumonic Plague still awaits solution.

Towards the close of the Great War, when economy of food consumption was an urgent necessity, considerable attention was paid to the determination of the energetic needs of various kinds of muscular work. The majority of scientific papers then published dealt with the problem.

1. The growth of diphtheria bacilli in suger-free pure casein digest broth may be accelerated by the addition of dilute nitric, acetic and lactic acids, and delayed by certain monobasic fatty acids.

2. The limiting acid zone for toxic and non-toxic varieties is unaffected by initial dilute acidifications by several acids, but incresaed by the addition of citric acid.

3. The time periods and intensity of the reaction changes produced by diphtheria bacilli growing in a sugar-free casein digest medium are altered by the addition of certain acids. Toxic strains produce earlier and more progressive alkalinity when dilute acetic or nitric acid is included in the medium: and later and lessened alkalinity in the presence of butyric, formic, and propionic acids. Certain other typical acids do not exert any obvious action. Non-toxic strains are less affected by the selected acids, although butyric acid generally retards reaction changes.

4. The time required for virulence testing is decreased, and the potency of the bacillus under examination is more evident when 1/200 η acetic or nitric acid is added to the culture medium. Acidified casein digest plus peptone broth yields practically the same results as acidified fermented veal peptone infusion. The acidification does not affect the metabolism of non-toxic strains.

5. The disadvantages of unfermented meat infusions and the ascribed harmful effects of the fermentation products in fermented meat broths, may perhaps be avoided by the substitution of casein digest peptone medium. The advantages of the starting action of the glucose may be retained by adding acetic or nitric acid to the casein digest.

6. Individual strains of diphtheria bacilli differ considerably in their capacity of altering the reaction of culture media, and in their toxic potency. It does not seem permissible to apply to newly isolated organisms all the published results obtained from cultures that have been repeatedly subcultured and established as toxin producers in nutrient bouillon. As a presumptive test in the virulence testing of bacilli just transferred from human tissues to artificial culture media the tendency of non-toxic strains to produce early formation of alkali in adequately buffered and adjusted unfermented veal broth may be thought worthy of extended trial.

Transbaikalia or Zabaikalia is a vast stretch of land lying to the north-west of Manchuria, bounded on the east by River Argun from China and on the west by Lake irkutsk and Irkutsk Mountains from the Irkutsk region. Its most important cities are Chita (capital), Stretinsk, Nerchinsk, Kiakhta and Borzia. The region around borzia for a hundred miles is composed of undulating hillocks inhabited by a species of large (cat-size) marmots or tarabagans (Arctomys bobac) whose skin is much sought after for the manufacture of imitation sable. The Russians and Buriats find the flesh of these animals whole-some, and often bunt them for the meat and the fat which they use for greasing shoes. It is among the trappers and eaters of tarabagans that the early case of bubonic plague are usually reported.

1. In the foregoing experiments evidence is adduced to show that bacteria in spleen broth or neutral Ringer's solution carry a negative charge and move to the anode in an electric field. The addition of a slight trace of a positive trivalent ion such as La or Ce or Yb to the solutions containing the bacteria immediately lessens or neutralises this negative charge, and if the concerntration of these ions is further increased completely abolishes it, and the bacteria undergo flocculation or agglutination. Living bacteria seem much more sensitive to the action of these ions than non-living colloidal particles. The addition of negative trivalent ions to bacterial cultures is without any effect on their movement in an electric field; the negative charge on the bacteria is not increased.

2. Some inconclusive evidence has been brought forward in support of Girard and Audubert's work regarding the influence of the double electric layer of the bacterial cell wall in controlling their biological properties.

1. An epidemic of diarrhoea or gastro-enteritis occurring in Aberdeen in 1919, and causing over 1000 cases and 72 deaths, has been proved to be due to infection of milk with dysentery bacilli of the Flexner type.

2. Similar epidemics of milk-borne diarrhoea have occurred formerly, but bacteriological investigation had failed to determine the nature of the infecting organism. Keference to the epidemiological and clinical features of such former epidemics, however, makes it practically certain that they were essentially of the same description as the Aberdeen epidemic of 1919, and accordingly indicates that they were likewise due to infection of milk with dysentery group bacilli.

3. The Aberdeen epidemic of milk-borne bacillary dysentery had run its course and had caused 72 deaths before serological proof of bacillary dysentery was available. Since the time of the Aberdeen investigation, notable advances have been made in methods for the bacteriological diagnosis of the dysenteries as a result of the fundamental work of F. W. Andrewes, A. D. Gardner, C. J. Martin and others. Nevertheless, modern methods of bacteriological diagnosis are not infallible, and the Aberdeen experience clearly indicates that deaths will be prevented if polyvalent anti-dysenteric serum and saline treatment are used at once in a disease having the clinical symptoms of bacillary dysentery, or in an acute enteritis from which has been isolated organisms with the cultural reactions of the dysentery group bacilli.

1. The experimental derivation of a mucoid form of B. paratyphosus B is described.

2. This form, though at one stage non-motile, agreed closely with the “capsulated mucoid forms” of paratyphoid B, isolated by W. Fletcher from two chronic “carrier” cases.

3. The mucoid paratyphoid B was highly dys-agglutinable, and it would not on serological examination be identified as a paratyphoid B.

4. Its colonies were also entirely unlike colonies of paratyphoid B, being large, slimy, and usually dome-shaped, though at other stages of their metamorphosis they presented either an umbilication, or a nipple-like elevation in the centre.

5. The mucoid bacillus possessed the distinctive sugar reactions of paratyphoid B.

6. On suitable manipulation it reverted to the ordinary form.

(1) Two types of B. coli are met with in urinary infections-haemolytic and non-haemolytic. Haemolytic colon bacilli are much commoner in infections in the male (72 per cent.) and non-haemolytic in the female (70 percent).

(2) It was very uncommon to obtain both these types of colon bacilli associated in any particular case, or for a haemolytic infection to be followed by a non-haemolytic, or vice versa.

(3) No evidence was obtained of direct relationship between the urinary haemolytic colon bacilli and those of the intestinal tract.

(4) The haemolytic urinary colon bacilli were readily grouped by appropriate colon anti-sera, but this result was much less common with the non-haemolytic strains.

(5) Culture media, in our experience, were of little value in the grouping of colon bacilli.

(6) A haemolytic colon bacillus has not been cultivated by us from the blood stream in the human subject.

(7) Two cases of acute infection were met with, caused by strongly haemolytic, but atypical, colon bacilli.

(8) The blood sera from “normal” cases and from coli infections were tested for the presence of coli agglutinins. Several coli antigens were employed. A very much higher percentage of positive findings were obtained with coli cases.

(9) Living colon bacilli, haemolytic and non-haemolytic, can be inoculated into rabbits in small or massive doses without serious ill-effect-in fact these animals have a remarkable tolerance for these organisms. No marked anaemia was produced by the injection of living or dead bacilli or filtered broth cultures. Agglutinins and precipitins were rapidly formed with the haemolytic strains.

(10) Eenal infections in rabbits were not obtained by the injection intravenously of various strains of urinary and faecal colon bacilli.

(11) Saturation agglutinin experiments showed in the majority of instances that colon anti-sera, made from non-haemolytic strains, are not desaturated by non-haemolytic colon bacilli other than autogenous strains, while with the urinary haemolytic colon anti-sera and haemolytic colon bacilli a much wider range of action is obtained.

(12) Precipitins and complement fixation reactions were readily obtained with coli rabbit anti-sera and filtered beef broth coli cultures.

(13) The action of No. 220 soluble mercurochrome was investigated in the treatment of coli infections of the urinary tract. This substance was found to be of definite therapeutic value, especially when employed in conjunction with vaccine therapy.

(1) The existence of sporadic cases of natural plague among tarabagans has again been established.

(2) The tarabagan is easily susceptible to pneumonic plague produced by the inhalation of B. pestis in spray form, and may contract, besides the acute infection, chronic type of the lung affection.

(3) Our inhalation experiments have proved contacts to be liable to pulmonary plague infection in both acute and chronic forms. The existence of carriers among tarabagans seems also probable.

(4) Tarabagans can be infected with plague by feeding upon artificially infected food, contracting an alimentary type of the disease. The B. pestis is easily cultivated from the intestinal tract of animals suffering from plague.

(5) Our evidence shows that subacute or chronic plague may exist among tarabagans in Mongolia and Siberia, and thus form a connecting link in the epidemiology of plague in those regions.