Stenosis of the Esophagus in Four Generations of Mice of the NH Strain *

The NH strain of mice was developed for the purpose of producing the highest possible degree of biological variability without the interfering incidence of spontaneous tumors. In order to do this, mice of three separate inbred strains were mated seriatim. The above strains were the CBA, the JK, and the N. Mice of the CBA strain have reached the forty-eighth generation of a pedigreed brother-to-sister mating. They possess the color genes for black and agouti (wild type). Mice of the JK strain carry the recessive genes for pink eye, short ear, brown, and non-agouti. They also possess an extra daw on one or both of their front feet and are devoid of a xiphoid process. They have reached the fortieth generation of pedigreed inbreeding. Mice of the N strain carry the recessive genes for pink eye, blue dilution, brown, non-agouti, and piebald. They have been inbred for thirty generations. Following the hybridization of mice from thesethree inbred strains, several pairs of F2 individuals were selected for the production of sublines. Among the various sublines established, one (NHS) is shown in the chart following. Two sisters of this descent (No. 136,876 and No. 136,877) were noted on Nov. 21, 1939, to be somewhat emaciated. Otherwise they appeared to be in good health. In doing routine autopsies, it was noticed that the esophagus in each of these two sisters was greatly distended with food (balloon shape) throughout the extent of the thoracic cavity, whereas immediately below the diaphragm the esophagus appeared contracted (cord-like), glossy-white, and firm. The rest of the gastro-intestinal tract appeared to be normal. On opening the distended part before fixation in 10 per cent formalin, it was found that the wall of the esophagus in this region was extremely thin and the lumen was filled with partly digested grumous milky food material, debris, desquamated epithelium, and strands of keratin. No perforations had occurred into the thoracic cavity nor were there any adhesions