PRACTICAL EXERCISES 609 



(2) Deeply etherize a dog or rabbit five hours after a meal rich in 

 carbo-hydrates e.g., rice and potatoes in the case of the 'dog. 

 carrots in the case of the rabbit. Fasten it on a holder. "Clip 

 off the hair over the abdomen in the middle line. Make a mesial 

 incision through the skin and abdominal wall from the ensiform car- 

 tilage to the pubis. The liver will now be rapidly cut out (by the 

 demonstrator) and divided into two portions, one of which will be 

 (distributed among the class and) treated as in (a) or (b) ; the other 

 will be kept for an hour at a temperature of 40 C., and then sub- 

 jected to process (a) or (b). Little, if any, sugar and much glycogen 

 will be found in the portion which was boiled immediately after 

 excision. Abundance of sugar will be found in the portion kept at 

 40 C. ; it may or may not contain glycogen. 



2. Catheterism. In many physiological experiments it is neces- 

 sary to obtain urine from the bladder by means of a catheter. It 

 is possible to pass a fine rubber catheter^ into the bladder of a male 

 dog. A larger one is easily passed in a male rabbit, and a still 

 larger in a bitch, which is often used for experiments on metabolism. 

 Even in the bitch the opening of the urethra lies entirely concealed 

 within the vagina, much deeper than the cul-de-sac in the mucous 

 membrane, into which the beginner usually tries to force the 

 catheter. For a first attempt the animal should be etherized and 

 fastened on a holder. The little or index finger of the left hand is 

 passed into the vagina till the symphysis pubis can be felt. A little 

 below this is the opening of the urethra. With the right hand the 

 point of a catheter of suitable calibre is directed along the finger, 

 and after a little ' guess and trial ' it slips into the bladder, its 

 entrance being announced by the escape of urine. A glass tube 

 drawn out to a sufficiently small calibre and bent near the point is 

 the easiest form of catheter to pass in a bitch. The point must, of 

 course, be rounded in the flame. 



When the bitch is to be used in a long series of experiments an 

 operation is sometimes performed first of all to render the urethral 

 orifice more accessible. 



3. Glycosuria. (i) (a) Weigh a dog (female by preference) or 

 rabbit. Fasten on a holder, and etherize. Insert a glass cannula 

 into the femoral or saphena vein of the dog, or into the jugular 

 of the rabbit (p. 200). Fill a burette with a 2 per cent, solution 

 of dextrose in physiological salt solution, connect it with the 

 cannula by means of an indiarubber tube, taking care that there 

 are no air-bubbles in the tube, and slowly inject as much of the 

 solution as will amount to \ or grm. of sugar per kilo of body- weight. 

 Tie the vein, remove the cannula, and in half an hour evacuate the 

 bladder by passing a catheter, by pressure on the abdomen, or, if 

 both of these methods fail, by tapping the bladder with a trocar 

 pushed through the linea alba (supra-pubic puncture). In an hour 

 again draw off the urine. Test both specimens for sugar. 



In this experiment the opportunity may also be taken to demon- 

 strate that egg-albumin, when injected into the blood, is excreted by 

 the kidneys, a filtered solution containing the albumin of one egg 

 and sugar in the quantity mentioned being injected. 



The catheter may be inserted before the injection is begun, and 

 the bladder evacuated. After the injection the urine that drops 

 from the catheter may be collectedFin test-tubes, first every two 

 minutes, and then, as soon as sugar is found, every ten minutes. 

 Determine the interval between injection and the appearance of the 



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