Renal changes were studied in rats with short and long-term alloxan diabetes. In the first few days, there was necrosis of cells lining the distal portion of the proximal convoluted tubules, with focal involvement of distal convoluted tubules, and was especially marked at the cortico-medullary junction. Not all tubules were equally affected. Disruption of the tubular basement membrane led to the formation of interstitial granulomas. Regenerating tubular epithelial cells were frequently abnormal, with basophilic cytoplasm and lacking a brush border. Regenerating cells were often flat or cuboidal, and sometimes they formed prominent clusters projecting into the dilated tubular lumen. Cystic tubular dilatation ensued in about 70 per cent of the cases and was very prominent in most of them, leading to a spongy appearance of the cortex. Tubular dilatation was probably due both to abnormal tubular cells and to incomplete tubular obstruction. These changes are different from chronic interstitial nephritis with which they were probably confused in the past. This lesion can be attributed to alloxan directly, with diabetes probably playing a secondary role by interfering with normal tubular regeneration.

Light cells in the hamster thyroid gland were examined by electron microscopy and histochemical methods in control, hypercalcemic and hypocalcemic animals. Elevation of plasma calcium levels stimulated a marked depletion of light cell granules as detected by electron microscopy and silver impregnation. In the hypercalcemic state the size and number of light cells did not differ from that of control animals. Hypocalcemic hamsters showed a significant increase in light cell numbers with marked hypertrophy and hyperplasia of this cell type. These observations support the view that the light cell in the hamster thyroid is associated with thyrocalcitonin secretion.

Reproductive decline in older female rodents has been interpreted as being due to deficiencies in various segments of the reproductive tract. Previous observations, such as those of Ingramamong others, have attributed deficiencies to one or all of the reproductive organs. In the present observations of a colony of aged females, examples of deficiencies at all levels of the reproductive tract were found. There were, however, a number of these animals which did produce a normal complement of ova and which fostered their continued development.Sixty-six virgin or multiparous rats, aged 18 months or older, were caged with males and matings were noted as having taken place by the presence of spermatozoa in the vaginal smear. The females were subjected to laparotomy or were killed at intervals from 1 hr following mating until term (Table 1). An additional fifteen rats, 18 months or older, were bilaterally ovariectomized. Three weeks after spaying, these females were started on hormone replacement therapy in the form of 2 mg progesterone daily.On Days 5 and 6 of progesterone treatment, each animal received 0-5 µg oestradiol propionate. On Day 6, needle stabs (six) were made in each uterine horn. On Days 9 and 10, the animals were killed. Most of the animals were injected with either Evan's blue or pontamine blue just before being killed to facilitate the observation of any decidual reactions.In thirty-five of sixty-six animals, evidence of pregnancy was observed (Table 1 ). Ova were found in the normal stages of cleavage and in the appropriate segment of the oviducts, with the following exceptions. Five of the twenty animals examined during the tubai period had a purulent salpingitis. Corpora lutea were absent in three rats. In two females, mating occurred after 09.00 hours. Ovulation was taking place in these two animals when they were killed 1 hr after mating.Thirty-six animals were examined on Days 4 to 9 of pregnancy. The uteri obtained during Days 4 and 5 (preimplantation stages) were serially sectioned. In the six negative cases, various degrees of leucocytic infiltration were found in the mesometrial segment of the lumen. In some, the migration of lympho¬ cytes was massive. Abnormal ova were surrounded by polymorphonuclear leucocytes. When implantation had occurred in the animals killed on Days 6 to 9 of pregnancy, the average number of decidual reactions per uterine horn 121

Spontaneous intersexuality in an adult rat, thought to be genetically male, has been described. Both male and female primordia developed concurrently and most components of each were retained with normal adult characteristics. Gonadal and hypophyseal hormones in this specimen stimulated ductal and lobulo-alveolar proliferation simulating that of the mammary gland during lactation.