Virus Passage and Passivity

VIRUS PASSAGE, the transmission of a microbe (resp. virus) through the organism of a susceptible animal for the purpose of increasing virulence; the method was first proposed by Pasteur. The animal is infected with the microbe; then it is killed or dies, and a pure culture is isolated from its organs, which is used to infect a new animal, repeating this procedure any number of times. It is also possible to passage organs by infecting an animal with a culture of the microbe and introducing an emulsion of the infected animal's organs into new animals. A pure culture is isolated only after a certain number of passages. The increase in virulence as a result of passage is obtained in relation to the animal through whose organism the microbe is conducted, but an increase in virulence in general is also often observed. In relatively rare cases, passage is performed not for the purpose of increasing, but for attenuating virulence; in such cases, the microbe is passaged through an organism that is little susceptible or even immune to the given infectious disease. Examples of passage for the purpose of increasing virulence: conducting pneumococcus through the organism of a white mouse, tubercle bacilli through the organism of a guinea pig, etc.; an example of passage for the purpose of attenuating virulence: conducting the syphilitic virus through the organism of monkeys (Metchnikoff), etc. The increase in virulence is explained from the point of view of natural selection by the survival of the most adapted individuals. Microbe passages take place not only under artificial but also under natural conditions, and in view of this, such passaging can acquire epidemiological significance. Thus, in the pre-aseptic era, the streptococcus, constantly passaged through the organism of women during puerperal diseases, acquired very significant virulence as a result; there is an opinion that prolonged passage of the tuberculosis pathogen through the human organism, which is relatively little susceptible to tuberculosis, entails an attenuation of the virulence of tubercle bacilli. PASSIVITY, a term used in psychoneurology to denote the absence of a desire to influence the environment. Passivity manifests itself both in the motor sphere, expressed in a lowering of muscle tone, a relaxed posture, and sluggishness of movements, and especially in the psychic sphere (lack of initiative, sluggishness of volitional impulses). Psychic passivity is associated with a decrease in the intensity of emotions and drives, as well as with a weakening of intellectual interests. Transient phenomena of passivity can occur during fatigue. Sharp motor passivity is observed during sleep and under anesthesia. A passive position of the limbs is characteristic in flaccid paralysis. Pronounced psychic passivity (usually also reflected in motor skills) is associated with a general lowering of biotonus and is observed in depressive states, schizophrenia, and especially in severe organic brain lesions: in tumors (especially of the frontal lobes), progressive paralysis, senile psychoses, epidemic encephalitis, etc. Often, states of passivity can be replaced by opposite phenomena of increased activity (for example, in traumatic lesions of the frontal lobes). Pathological passivity should apparently be considered one of the manifestations of the frontal syndrome. Within the limits of normal variations of the psyche, passivity can be a characterological trait resulting from the peculiarities of the subject's biotonus.