Problems involved with the efYects of self contamination of the containing water upon various phases of physiology, especially on growth of aquatic organisms, have been worked upon f o r almost 90 years. The general results obtained, together with many details, havc been summarized elscwhcre (Allec, '31, '34, '38). The first of this experimental work was iipon snails (Hogg, 1854) ; experimentalists soon became interested in various phases of crowding in connection with experimental populations of fish and for obvious reasons this interest has tended to increase.With fish, as with most other animals studied, it is relatively easy t o demonstrate various retarding effects of a high degree of self contamination and here, as elsewhere, the more elusive problem has been to find the opposite type of result, if any, from smaller amounts of such homotypic conditioning. Five reports of investigations dealing with different aspects of this problem have becn issued from this laboratory (Shaw, '32 ; Allee, Bowmi, Welty and Oesting, '34; Allee, Oesting and Hoskins, '36 ; Evans, '36 ; Livengood, '37). The present report is a direct continuation of the second and third of these papers.The 1934 paper reported the results of thirteen comparable expwiments with young goldfish (Carassius auratus) in which 177 goldfish in water which had been conditioned by having other goldfish live in it, showed a mean increase in length ofWe are indebted to Mr. Wayne Livengood for permission to use unpublished data from experiments performed by him while he was working in this laboratory.
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to that of cortical bone but differs in degree of a~t i v i t y .~ The 2 scarred teeth were split in such a way as to isolate the part containing the grooves and estimations were made both on this and the remainder of the tooth. There was no difference between the P* contents of the scarred and the unscarred parts. Within the 12day experimental period, there was evidently no increase of phosphate turnover or deposition in response to the stimulus of scarring.Several attempts were made to find evidence of the presence of P* in the enamel. In no case was a count obtained which was more than 0.2 or 0.3 counts per minute above the background count. This difference is either insignificant, showing no P* to be present, or indicates that the enamel contained less than 0.001% of the original P* dose. The disagreement with the findings of Hevesy and Armstrong may be due to the larger doses used by these workers. In a private communication, Armstrong indicated that with similar sized doses of P* he had found questionable evidence of P* in cat enamel.Sumnzary. The uptake of radioactive phosphorus was greater in spongy than in dense diaphyseal bone when salts of the element were administered orally to a dog. In dentine the amounts of radioactive phosphorus were constant for the various teeth and of the same order as that present in dense diaphyseal bone. No more than traces of P* were found in the enamel.
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