Tot Hurt Critically In Crash A 27-month-old boy, Robert Avila of Piedras Negras, Coahuila, Mexico, was in critical condition at St. Mary's Hospital this afternoon afternoon with head injuries suffered in a two-car collision on North 6th ave. at Drachman St. Of the five persons examined at the hospital, the boy was the only one seriously hurt. Attendants said x-rays showed no skull fracture, but he lapsed into convulsions and was placed on.the critical list after preliminary examination. The child's mother, Mrs. Dora Avila, 23, same address, was released released after emergency treatment for cuts and bruises. Another member of the Mexican family, Tony Chavez, 14, had only minor injuries and was also released. Otricers said the three were passengers in a 1949 coupe with California license plates passing through Tucson en route to Mexico via El Paso. The car was hauling a two-wheel cargo trailer loaded with the family's household goods, which were strewn on pavement by the impact. Driving the eastbound California car was Mrs, Avila's brother, Mateo C. Valles, 19, an itinerant laborer who gave his address general delivery, Eagle Pass, just across the international boundary boundary from Piedras Negras. Valles was cited for running a boulevard stop and failure to yield the of-way. The second auto was driven Carlos G. Sanchez, 25, of 216 E. Lee St., who was headed south on 6th avenue. Officers said Sanchez' Sanchez' vehicle skidded 19 feet before before striking Valles' auto on the left side. Sanchez and his wife, Blanca, 22, were released after treatment at St Mary's for cuts and bruises.