, but a few earlier papers have been referred to when necessary. In the section devoted to pasteurisation machinery has been dealt with, but only in so far as its efficiency has been assessed by bacteriological methods. The study of pathogenic organisms as such, does not come within the scope of this review.
The characters are given of the organism causing the “coconut” or “carbolic” taint of commercial sterilised milk. Although certain similarities with B. novus (Plectridium novum) Huss are shown to exist, the organism remains unidentified and the question of its identity has been reserved for a subsequent paper.In laboratory culture the organism exists in a stable vegetative form which has resisted all efforts to induce it to sporulate. Under commercial conditions, on the other hand, it occurs in a spore form in the bottles of tainted sterilised milk.Propagated by ordinary laboratory methods, the spore form is rapidly replaced by a vegetative race. Five serial transplants are sufficient to bring about this transformation.Sporulation can be induced and maintained indefinitely if sporing cultures are heated at 100°C. for 30 minutes at the time of inoculation. The function of the heating process appears to be the destruction of a growth product inhibitory to the germination of the spores. This substance is associated with the growth of the vegetative form and its presence in unheated cultures is inhibitory to the germination of the spores.Spore formation takes place at temperatures below 22°C., the spore cycle occupying 3 days at 22°C., 6 days at 15°C., and 15 days at 5°C. At higher temperatures, e.g. 30 and 37°C., it is inhibited and the normal process is replaced by an abortive effort at spore formation. The optimum temperature for the propagation of the spores is 22°C.
In the foregoing parts it is indicated that great difficulty may be experienced in the control of the spoilage of commercial sterilised milk which results from the development of spore-bearing bacteria.A detailed study of the actual sources of contamination is now being made, but in the meantime it may be pointed out that many of these bacteria are typical members of the soil flora. They may therefore enter the milk from the dust either at the farm or the factory. The greater the care with which the milk is handled from the time of milking until the end of the heating process, and the greater the efficiency of the cleaning and sterilisation of the plant and the empty bottles, the less will be the danger of spoilage arising from the use of infected milk. During the course of the investigations recorded it has been necessary to carry out numerous control experiments. The milk used has been Grade A (T.T.) milk and the utensils with which it came into contact and the empty bottles into which it was poured were clean and sterile. There has never been the least difficulty in obtaining a sterile, fresh-smelling and sweet-tasting product after heating at 100°C. (212°F.) for 30 minutes and storing at 22°C. (72°F.).
(With 1 Chart) INTRODUCTION IN a series of publications issued from the Institut Prophylactique in Paris, Vernes and his co-workers (1926) described a flocculation method for the diagnosis of tuberculosis in man. This method was first elaborated for the diagnosis of syphilis. Various modifications were then introduced and it was found that the test could be applied to the diagnosis of human tuberculosis. Finally a standard technique was laid down. This consisted of measuring by means of the Vernes-Bricq-Yvon photometer the amount of flocculation which took place during 4 hours' incubation at 20°C. when 0-6 c.c. of resorcinol (1-25 per cent.) was added to an equal volume of the blood serum under test. Readings were taken immediately the resorcinol was added and again at the end of the incubation period. The difference between these readings gave the value on which the diagnosis was made. If this were below 30 the serum was considered normal. Values over 30 indicated infection, the higher the number the more advanced the infection. Correlation of these figures with clinical examination showed that very frequently the photometer value confirmed the clinical findings, and that in some cases the course of the disease could be forecast and followed by testing a number of blood samples over a period. Boyer and Placidi (1931) reported that, using the identical technique described by Vernes for human tuberculosis, it had been possible to diagnose with a high degree of accuracy tuberculosis in bovine animals. Values of over 30 were recorded in 80 per cent. of the tuberculous sera tested, whilst in 77 per cent. of the normal sera the readings were less than 10.The diagnosis of tuberculosis in cattle in this country depends almost entirely upon the tuberculin test in one or other of its forms. This test is known to give good results where the disease is well developed, but where the case is a border-line one the results are often misleading. The doubtful reactor is therefore a problem in tuberculin-tested herds, and any test which could give definite information in such cases would be extremely valuable. In view of the excellent results reported by Boyer and Placidi, it was decided to investigate the Vernes test in this respect.The importance of testing only authentic sera was realised at the outset. Three groups were therefore set up and only sera which belonged strictly to one of these were used.
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