The application of pure cultures of bacteria for improving the fertility of the land is still in an experimental stage.
P. donovani in cultures of different ages.
The various tissues affected are examined microscopically and cultures made from them; in this way the structural changes and the relation of bacteria to them can be determined.
Cultures of the typhoid organism planted at a depth of 18 in.
Long before history begins, however, the cultures of Eridu and Nippur had coalesced.
Experiments show that pure cultures, when mixed with garden soil constantly moistened short of saturation and kept in the dark at a temperature of 14° C., will retain their vitality for more than ten months; from moist soil kept at 26° C. they die out in about two months; from moist soil at 30° C. in seventeen days; and in dry soil at the same temperature within a week.
The observations Bacteria g 5' of Downes and Blunt in 1877 left it uncertain whether the bactericidal effects in broth cultures exposed to solar rays were due to thermal action or not.
Pure Cultivation of Yeasts.-The methods which were first adopted by Hansen for obtaining pure cultures of yeast were similar in principle to one devised by J.
In early inquiries a great point was made of the prevention of putrefaction, and work was done in the way of finding how much of an agent must be added to a given solution, in order that the bacteria accidentally present might not develop. But for various reasons this was an inexact method, and to-day an antiseptic is judged by its effects on pure cultures of definite pathogenic microbes, and on their vegetative and spore forms. Their standardization has been effected in many instances, and a water solution of carbolic acid of a certain fixed 'strength is now taken as the standard with which other antiseptics are compared.
But by a process of successive and continued artificial cultures under different conditions, the virus of the organism is found to become attenuated; and when this weakened virus is administered, the animal is rendered immune against further attacks.
- According to a conception of the world frequently found among peoples of the lower cultures, all the affairs of life are supposed to be under the control of spirits, each ruling a certain element or even object, and themselves in subjection to a greater spirit.
Wright and others, in recent work on opsonins, have shown that, by injecting dead cultures of the causal agent into subjects infected with the organism, there is produced in the body fluids a substance (opsonin) which apparently in favourable conditions unites with the living causal bacteria and so sensitizes them that they are readily taken up and destroyed by the phagocytic cells of tissues.
But in the admixture of the two cultures the influence of Eridu was predominant.
Pure cultures may be made and after dilution in water or other liquid can be mixed with soil to be ultimately spread over the land which is to be infected.
More or less pure cultures of the nitrogen-fixing bacteria belonging to the Azotobacter group have been tried and recommended for application to poor land in order to provide a cheap supply of nitrogen.
The organization of the French colonies, though industrially ruinous, gave them Illustrations representative of the primitive cultures of Central America, Mexico and Peru (q.q.v.) selected and arranged by Dr Walter Lehmann of the Royal Ethnographical Museum, Norwich.
The most favoured areas were those where corn and other plants could be artificially produced, and there barbaric cultures were elaborated.
Schuppan has shown that it is possible to produce good butter from Pasteurized or even sterilized cream, and Weigmann introduced the plan of artificially souring cream by means of pure cultures of B.
Nevertheless, the general appearance and structure of these motile forms so greatly resemble that of a Herpetomonad, or of the " pseudo-Herpetomonadine " forms of a Trypanosome which are obtained in cultures, that it cannot be doubted that the " Leishman-Donovan-Wright " bodies are closely connected with the Haemoflagellates.
In favour of the conidial view is the fact that in the case of Collema and a few other forms the spermatia have been made to germinate in artificial cultures, and in the case of Calicium parietinum Moller succeeded in producing a spermogonia bearing thallus from a spermatium.
The work is carried on from October till the end of March and April, after which, with the exception of melons, the cultures are carried on in the open air.
The group has attained an importance of late even beyond that to which it was brought by Pasteur's researches on alcoholic fermentation, chiefly owing to the exact results of the investigations of Hansen, who first applied the methods of pure cultures to the study of these organisms, and showed that many of the inconsistencies hitherto existing in the literature were due to the coexistence in the cultures of several species or races of yeasts morphologically almost indistinguishable, but physiologically very different.
The principal cultures are tobacco, maize and cotton, and the mulberry for silk production.
For the mainland cultures a new term " Helladic " has lately been invented, and three chronological divisions, Early, Middle and Late Helladic, are proposed to correspond with the parallel Cycladic and Minoan periods.
What is chiefly sought by such revision is better evidence for the chronology and inter-relation of the different cultures, but much new information has been gained in regard to plan and structure of the palaces and fortifications of Mycenae and Tiryns.
After a lengthy development in the history of the human race a definite stage seems to have been reached about 5000 B.C., which step by step led on to those great ancient cultures (Egyptian, Aegean, Babylonian) which surrounded Palestine.
The earliest victim was an attendant named Barisch, employed in the pathological laboratory of the Vienna General Hospital, and told off to look after the animals and bacteriological apparatus devoted to the investigation of plague, cultures of which had been brought from India by the medical commissioners sent by the Royal Academy of Science in 1897.
The Bombay Plague Research Committee, whose experience is unequalled, say: " In a number of instances points of inoculation were found on the extremities of patients, from which plague cultures were obtained, and in these cases buboes were found above the point of inoculation.
It is especially desirable for hospital and ambulance staffs to be inoculated with a vaccine prepared from sterilized cultures of plague bacillus.
In this way, by making pure cultures derived from some of the finest French and German wines it has been possible to lend something of their character to the inferior growths of, for instance, California and Australia.
In the same way sterilized cultures of typhoid bacilli have been used to protect against attacks of typhoid fever, and an anti-typhoid serum has been employed with intent to cure.
It has been found possible to grow pure cultures of various diatoms, and by feeding these to delicate larvae kept in sterilized sea-water, great successes have been attained.
It appears from the observations of Maze that the bacterium can even absorb free nitrogen when grown in cultures FIG.
A definite bacillus to which the peculiarly fine flavour of certain butters is due, is said to be largely employed in pure cultures in American dairies, and in Denmark certain butters are said to keep fresh much longer owing to the use of pure cultures and the treatment employed to suppress the forms which cause rancidity.
It was formerly supposed that the injection of attenuated cultures or dead organisms-vaccines in the widest sensewas only of service in producing immunity as a preventive measure against the corresponding organism, but the work of Sir Almroth Wright has shown that the use of such vaccines may be of service even after infection has occurred, especially when the resulting disease is localized.
Cultures are made by transferring by means of a sterile platinum wire a little of the material containing the bacteria to the medium.
Subsequent cultures or, as they are called, " subcultures," may be made by inoculating fresh tubes, and in this way growth may be maintained often for an indefinite period.
Such cultures are called " deep cultures."
To obtain growth of an anaerobic organism on the surface of a medium, in using the plate method, and also for cultures in fluids, the air is displaced by an indifferent gas, usually hydrogen.
Cultures of varying degree of virulence may be obtained by such methods, and immunity can be gradually increased by inoculation with vaccines of increasing virulence.
The immunity may be made to reach a very high degree by ultimately using cultures of intensified virulence, this " supervirulent " character being usually attained by the method of passage already explained.
Confined to higher cultures on the other hand, for obvious reasons, is divination by automatic writing, which is practised in China more especially.
Dr Maassen records a case where he had no difficulty in obtaining cultures from spores removed from combs after being kept dry for twenty years.
Only those cultures which contained a single yeast speck were assumed to be pure cultivations.
For purposes of inoculation young vigorous cultures must be used.