Abstract
In former investigations we 1 studied the influence of acid extracts of anterior pituitary gland of cattle on the growth of bone and cartilage in young guinea pigs. We analyzed the endochondral ossification in normal animals as well as the callus formation in guinea pigs in which a bone had been fractured; we could establish under these conditions a growth-promoting effect of the anterior pituitary extract. In about 20% of the cases the growth of both cartilage and bone was stimulated to the same extent, with consequent hypertrophy and hyperplasia of their various cells. However, in the majority of the animals the process of ossification predominated over the formation of cartilage, thus causing an earlier closure of the epiphyseal line than would have taken place otherwise.
The question arises now as to the mechanism by which the extract exerts its effect on bone and cartilage, in particular, whether the pituitary hormone acts directly on bony and cartilaginous tissues or whether it exerts its effects indirectly by way of the thyroid.
Loeb and his collaborators 2 had tested the effects of the anterior pituitary extracts in thyroidectomized guinea pigs in order to determine whether certain actions of the extract depend on the changes produced in the thyroid gland or whether the extract affects the various organs directly.
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