. Annals of the New York Academy of Sciences. Science. SCOTT, STUDY OF CHANGES IN illSTELVS CANIS 33 Table XIII.—Change in A of hlood of Squalus acanthlas after immersion in fresh ivater for one hour No. Length in cm. Rise in A alter .30 minutes in fresh water Rise in a after (JO minutes in fresh water 1 2 3 4 56 58 61 61 +° + + + +° + + + f The average change during the first half hour is +° and at the end of an hour amounts to +°. At the end of the same period in fresh water the blood of Mustelus had changed about °. At first i
. Annals of the New York Academy of Sciences. Science. SCOTT, STUDY OF CHANGES IN illSTELVS CANIS 33 Table XIII.—Change in A of hlood of Squalus acanthlas after immersion in fresh ivater for one hour No. Length in cm. Rise in A alter .30 minutes in fresh water Rise in a after (JO minutes in fresh water 1 2 3 4 56 58 61 61 +° + + + +° + + + f The average change during the first half hour is +° and at the end of an hour amounts to +°. At the end of the same period in fresh water the blood of Mustelus had changed about °. At first it might be thought that the smaller change in the spiny dog-fish indicates an acquired immunity to the effects of dilute solutions of sea-water. It is possible that the limiting membranes of the body have become less per- meable, thus preventing such a great change as in the blood of Mustelus^ in the experiments with which the change in the external medium was greater. But, as was claimed above, the A of the blood of Squalus has risen °, due to the difference be- tween the molecular concentration of sea-water and harbor water. Moreover the freezing point of its blood has risen an additional °, due to the trans- ference of the fish from harbor water to fresh water. The total change is thus °, or nearly as great as that taking place in the blood of Mustelus, which was transferred directly from sea-water to fresh water. If this equality of modification in the osmotic pressure of the blood be true, then it follows that the limiting mem- branes of Squalus have acquired little or no resistance to the external medium; for their permeability has not changed. The change in the osmotic pressure of the blood is still proportional to the change in the osmotic pressure of the external medium. In Fig. 3, the point E, on line C—D, represents the A of the blood of Squalus from harbor water, which has a A of about °. Fig. 6 shows the changes in A of blood of Squalus
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectscience, bookyear1877
