236 LIFE: ITS NATURE AND ORIGIN 



of "crossing over" in the chromosomes bespeaks their soft, quasi- 

 gelatinous nature, which permits them to break apart and re- 

 cement themselves in new arrangements. Whatever truth there 

 may be in the popular belief that a blow, on the tender and 

 hydrous tissues of the breast, for example, may sometimes lead to 

 a cancer, might become understandable on this basis of traumatic 

 fracture of a harmless or useful catalyst area followed (fortunately 

 rarely) by the formation of a harmful one. Experiments with 

 localized and not too violent ultrasonic vibrations represent an 

 experimental approach to such questions. 



There is evidence that a virus, entering the body as an infective 

 agent, may persist there and be transmitted to progeny, possibly 

 forming a persistent addition to the self-duplicating units of the 

 cytoplasm of body cells, or of the body fluids. Mice experimentally 

 inoculated with a non-fatal dose of choriomeningitis virus develop 

 an immunity in 5 to 7 days and rapidly become free of demon- 

 strable virus. Pregnant mice when inoculated seem to pass the 

 virus on to their offspring, which develop after birth almost as 

 normal mice, but continue to carry the virus and pass it on to 

 their progeny. 40 Dr. Charles Armstrong reported 41 that a strain 

 of choriomeningitis virus had been passed "in an unbroken series 

 from an infected mother through 1 1 generations of her offspring 

 with no apparent tendency of the virus to weaken or disappear. 

 It has also been observed by Haas 42 that these congenitally infected 

 mice are far more efficient transmitters of the disease to normal 

 cage mates than are mice inoculated after birth." Probably mice 

 develop antibodies against the virus antigen. Furthermore, we 

 have here evidence for a non-genic inheritance mechanism. 



Plant Galls and "Plant Cancers" 



Inoculation of a host plant with the bacterium Phytomonas 

 tumorjaciens produces "crown gall." In the case of sunflower 

 plants, true secondary tumors developed several internodes away 

 from the primary tumor. 43 On confirming this work recently, 

 P. R. White and A. C. Braun found that the secondary tumors 

 were generally sterile, and their tissues could breed true in vitro 

 in a medium which remained bacteria-free, even though capable 

 of supporting a profuse growth of the gall-initiating Phytomonas 

 tumorjaciens. These authors conclude that the affected tissues 

 have undergone a drastic change, indicated (1) by the abnormal 

 capacity to produce galls, and (2) by their abnormal growth habits 



