ONE CHART
A unique strain of inbred albino rats has been produced at
The Wistar Institute, Philadelphia, by Dr. Helen Dean King, who in the year 1909 took a normal, healthy litter consisting of two males and two females from the standard colony of the Institute and mated them as two pairs. Brothers and sisters from the same litter were taken from their progeny and again mated, and this process of mating litter-brothers and -sisters has been continued without interruption up to the present time. The individuals selected for mating have in all cases been the largest and most vigorous of those available, any weaknesses originally represented in the strain thus being eliminated. The details of procedure and the results in respect of body weight, fertility, vigor, and sex ratio up to the twenty-fifth generation were reported by King ( '18, '19), and showed that, with the amount of selection indicated above to avoid the concentration of any recessive defects or weaknesses represented in the strain, close inbreeding in itself did not have any deleterious effects. The treatment of the more recent generations has not diverged from that accorded to their predecessors, as described by King in the papers cited.
The present communication has to do with the results of studies on the vascularity of certain parts of the central nervous system in some of the inbred rats produced by Doctor King.