^ 



and Laboratory Methods. 1T1>5 



UREA. 



Urea is always present in urine of any reaction. Normally 

 about '2 per cent, of the urine is urea. If less than 2U grams, 

 about 300 grains, or more than 30 grams, about 450 grains, of 

 urea are passed in 24 hours it should attract attention. 



The Doremus method of determining the amount of urea is 

 satisfactory and simple. A Doremus ureometer and the fol- 

 lowing solutions will be required : Doremus Iriometer. 



Caustic soda C. P. - - 100 grams. (, 1.540 grains ) 



Distilled water - - - 250 c. c. ( S^i^ oz. \ 

 Mix and allow to cool. 



Bromine - - - - 25 c. c. (1 oz.j 



Take of the caustic soda solution 10 c. c, add to it 1 c. c. of bromine, meas- 

 ured with the pipette accompanying the ureometer. Mix thoroughly and add 

 10 c. c. of distilled water. Pour the mixture, which is a freshly made solution of 

 hypobromite, into the ureometer, inclining it so that the upright part will be filled 

 completely. By means of the curved pipette introduce 1 c. c. of the urine into 

 the upright portion of the instrument so that the gas as formed may not escape, 

 but be collected at the top. The readings are made directly from the gradua- 

 tions, which may be in grains per ounce or in grams per litre. In this latter 

 case the figures .01, .02, .03, etc., mean 1 per cent., 2 per cent., or 3 per cent, of 

 each litre of urine is urea — ^i. e., there are 10, 20, or 30 grams of urea per litre 

 of urine. Urea is increased in febrile diseases, acute rheumatism, acute nephri- 

 tis, congestion of the kidneys, before convulsions of pregnancy, etc. It is 

 decreased in chronic nephritis, anemia, diabetis, insipidis, etc. 

 Harvey Medical College. WiLLIAM H. Knap. 



The Technique of Biological Projection and Anesthesia 



of Animals. 



CoPVKIGHTED. 



III. SOLAR PROJECTION APPARATUS AND ITS ADJUSTMENT. 



In dealing practically with the subject of biological projection, one of the 

 first problems to arise is, in many cases, the cost of the necessary apparatus. It 

 is appropriate, therefore, that the first type to be described should be the least 

 expensive. Moreover, it is possible to construct, at very little cost of time and 

 money, a simple but useful porte-lumiere which, in connection with a reasonably 

 good microscope, will project excellent living charts and prove equally useful in 

 chemical and physical experiments. To illustrate, having on hand a cheap plano- 

 convex condenser four inches in diameter and a fairly good microscope 

 with inclination joint, a projection apparatus was constructed at a cost of about 

 two and a half dollars. The exhibitions given with the apparatus during a period 

 of years covered quite a wide range and included successful attempts at some of 

 the difficult problems. If purchased complete, a good porte-lumiere is not very 



