Most of rural people in Iran living in small villages were subsisting on small scale farming or animal husbandry in an arid environment. Farms and houses belonged to the landowners (malik or arbab) who lived usually in urban places. That is, most of inhabitants in villages were sharecroppers (ra'iyat) or share-tenants (ijareh-Kunandeh) and their families. They were largely dependent on the landowners or landlords not only economically but also socially even after the Land Reform, which started in 1963 and had apparently cleaned out share croppers and share-tenants. On the other hand, both urban and rural population of Iran increased rapidly after the World War II, and migration from rural areas to urban places was also noteworthy. The migration is thought to be stronger related to limitation in population carrying capacity of the villages The author had a survey trip to a village on the north slope of the Zagros mountains. and investigated the effects of socio-economic stratification on the population carrying capacity of the village as well as the capacity of the families for sustaining their members.
The nulliparous female (12 weeks old, ddN strain) were used. The mice were intra-peritoneally administered with single injection of NiCl2 solution on the day 7, 8 and 9 of gestation. Four different levels of dosis were injected as follows : namely 2.2, 3.3, 4.5, and 5.6mg/kg (as Ni) which correspond to 1/10, 1.5/10, 2.0/10 and 2.5/10 of LD50 of adult mice respectively. The mothers were killed on the day 18 of gestation and their uteri were examined for implantation and resorption sites. Each fetus was weighed and examined for external anomalies. Skeletal preparations staind with Alizarin Red were also examined. The higher the dose increased, the more the resorptions and fetal deaths occurr ed among groups injected with NiCl2. Fused ribs and/with fused vertebral relationships archs were observed among groups injected with NiCl2 according to positive dose-response and those occupied 79 % out of malf ormatons as a whole. The highest rates of skeletal anomalies were observed in the case of groups injected on the day 9 of gestation compared with the groups injected on the day 7 or 8 of gestation at any level of dosis. Retardation of process in ossification was observed among fingers, toes, taluses and calcaneuses. Though the number of mother mouse is not sufficient, the incident rate of anomalies of fetal mice was so remarkable that the existence of teratogenic action of Ni can be proved. And through the experiment, it can be said that there exist developmental stage specificity to the action of Ni and agent specificity for the adverse influence to the fetal mice. There must be performed further detailed observation to make more statement on this theme.