The effect of light and of darkness on some urinary and blood constituents in the dog.

As a part of the general problem of the influence of light on “normal” animals, a study is being made of changes induced in dogs subjected to longer or shorter successive periods of darkness and of light. At the present time we desire to report a series of results on certain chemical constituents of blood and urine.

Two female dogs, M and G, were brought into the laboratory on November 10, 1923, and placed in large metabolism cages. Dog M was a full grown adult weighing 17.2 Kg., while dog G was about a year old, weighing 12.8 Kg. The room in which the cages were kept was well ventilated and lighted, having a southeastern exposure. Temperature was read on a maximum and minimum thermometer, and registered a maximum variation of 4°C.; while wet and dry bulb readings showed the humidity to be constant.

The diet used was that recommended by Cowgill 1 supplemented by 40 mg. per kilo of Harris yeast vitamine powder made into special tablets containing 50 mg. vitamin extract and 50 mg. inert starch. The diet (see Table I) furnished 80 calories per kilo body weight, and has been shown to be ample for the maintenance of dogs under ordinary laboratory conditions.

The dogs were allowed to become accustomed to the food and surroundings, until analyses of urine and blood indicated nitrogen balance. Catheterization was done daily with due precautions against infection. Usually the urine was analyzed immediately. When this was impossiblle the sample was covered with toluene and kept in the refrigerator. The cages were cleaned daily to prevent contamination of the urine by hair and feces. When desired for analysis, blood was drawn from the femoral artery under oil, immediately after catheterization.