SERUM PROTEIN MEASUREMENTS IN THE LOWER VERTEBRATES. I. THE COLLOID OSMOTIC PRESSURE, NITROGEN CONTENT, AND REFRACTIVE INDEX OF TURTLE SERUM AND BODY FLUID

¹ From the Physiological Laboratory, Mount Holyoke College, South Hadley, Massachusetts

The average serum colloid osmotic pressure of two normal fall turtles of the species Malacoclemmys geographica, Les. was 96 mm. water pressure. This pressure was lowered by starvation, especially at laboratory as compared with winter temperature, but the serum protein concentration was much less affected. A body fluid obtainable from about half of the animals showed a colloid osmotic pressure of more than half the serum pressure in these individuals, though the protein content was low. These findings are interpreted as indicating that in this species the colloid osmotic pressure may not be the only controlling factor in the water balance between blood and tissues, and that other functions of plasma proteins may be of importance.