Differences in growth pattern of bone and incisor of rats exposed to O 2 atmospheric and high pressure.

Three groups of young rats (age 22 days) were exposed intermittently (49 times), over a period of 44 days, group 1 to O2 at atmospheric pressure (OAP), group 2 to O2 at high pressure (OHP) (60 psig) and the third to air at atmospheric pressure (AAP) as controls. The average food consumption for the AAP group was 18.85 g, for the OAP 17.55 g and for the OHP 17.07 g per rat per day. The change in the body weights of each of these groups was followed throughout the experiment which continued 13daysafter thelastexposures.Bonegrowthofthemaxilla, mandible andfemur diaphysis and incisor growth were not altered by the OAP exposures, but were decreased by the OHP exposures; incisor growth, however, was increased. Hardness of the bone (by Tukon Hardness Tester) was increased in the OAP and OHP exposures as compared with that of the AAP, but the hardness of the incisors was not altered.