Few babies under six months catch measles, scarlet fever, diphtheria or infantile paralysis. Why, asked Drs. Charles Fremont McKhann Jr. & F. T. Chu of Harvard's pediatrics department.
Other investigators think the infants get their immunity from their mother's blood or milk. But there are arguments against that conception. A more tenable theory: the rapidly multiplying fetal and infant cells may establish a general protection called ''tissue immunity." If so, opined Drs. McKhann & Chu, the placenta (afterbirth) must contain substances which would prevent measles, scarlet fever, diphtheria and infantile paralysis in...