Nasal Salt Excretion and the Possible Function of the Cloaca in Water Conservation

Secretion of concentrated salt solutions from the nasal region was observed in several terrestrial birds and reptiles. In the secreted fluid potassium usually exceeded sodium concentrations, with chloride and bicarbonate as the major anions. It is suggested that the extrarenal excretion of salts is related to the reabsorption of water in the cloaca, that it is necessary for the production of urine with a particularly low water content, and perhaps was prerequisite for the evolution of efficient cloacal water conservation.

Kidney Function in the Crab-Eating Frog (Rana Cancrivora)

1. A study has been made of kidney function in the crab-eating frog, Rana cancrivora, of south-east Asia.

2. This frog can live in full-strength sea water; in such concentrated media its blood is slightly hypertonic to the medium, and a considerable part of the osmotic concentration is due to urea.

3. In concentrated media the excretion of urea is greatly diminished. This is not due to active tubular reabsorption of urea, but primarily to a low urine flow caused by increased tubular reabsorption of water and reduced glomerular filtration.

4. In concentrated media, as compared with dilute media, only a few percent of the filtered urea appears in the urine.

5. Osmoregulation of the crab-eating frog in sea water resembles that of elasmobranchs except in that there is no evidence of active tubular reabsorption of urea in the frog.

PHYSICAL INSULATION OF HEALTHY MEN AND WOMEN OVER 60 YEARS

Maximal body insulation [ I = (rectal temp. – skin temp.)/rate of skin heat loss] of healthy Korean men and women (17 each) over 60 years of age was determined by a method applied earlier to diving women of Korea (Rennie et al. J. Appl. Physiol. 17: 961, 1962). The critical water temperature was similar for males and females, ranging from 28–33 C. The water temperature at which 50% of subjects shivered was 31.2 C for both groups. This value is identical to that of young Korean men but is significantly higher than that of young Korean women. When a comparison was made at 31 C water, the extent of reduction in rectal temperature was, in the aged group, greater in males than in females, and was also greater in the aged than in the young. However, these differences could be accounted for mostly by the difference in subcutaneous fat thickness. When the values of I were considered as a function of the subcutaneous fat thickness, there was no difference either between old males and females or between the aged and young Korean subjects. This indicates that maximal body insulation due to physical factors does not change as a function of age.

Note:

(With the Technical Assistance of Jin Kyung Kim)

temperature regulation; aging process; subcutaneous fat; cold; shivering threshold

Submitted on January 15, 1964

Influence of Degree of Intentional Learning upon the Performance of an Incidental Task

Incidental learning was measured at various stages of intentional learning. Results indicated the best performance on the incidental learning task took place at the initial and terminal stages of intentional learning. It was hypothesized that Ss respond to a number of irrelevant stimuli at the onset of a problem, thereby experiencing more of the problem's incidental aspects. As behavior becomes increasingly dependent upon relevant cues, sampling of the irrelevant (incidental) cues is minimized. Incidental learning decreases, therefore, Ss training increases. This process occurs to a point, then reverses. When the task set by E is seen as mastered, S begins seeking additional information from the stimuli present, resulting again in considerable incidental learning. The results and proposed explanations were believed to be in accordance with an earlier study by Bahrick (1957).