146 URINARY APPARATUS. 



containing a mixture of eight parts of common alcohol, and 

 two parts of hydrochloric acid. The flask is fitted with a cork, 

 through which a very long glass tube passes. It is kept 

 boiling for some hours, after which the liquid is poured away, 

 and replaced by distilled water. In this liquid (which should 

 be changed once or twice) the portions of kidne} T are steeped 

 several da} f s. They are then agitated in a test tube, contain- 

 ing a little water, by which means the tubes readily separate 

 from each other. They can now be prepared in the same 

 liquid for microscopical examination, or allowed to subside, 

 and then separated from the liquid and mounted in glycerin. 

 Pure hydrochloric acid is also used for the same purpose. 

 The slices of kidney, which must be taken from an animal 

 killed the day before, are steeped in hydrochloric acid of 1-120 

 sp. g., for five to twenty hours. Thereupon the portions are 

 carefully washed with distilled water. Of these methods, the 

 former is easier. By either it can be shown that the capsule 

 of the Malpighian body is first contracted, and then dilated so 

 as to form the convoluted urinary tubes, which are filled with 

 a substance, the division of which into cells is almost indis- 

 tinguishable. These tubes are continued onwards, first as the 

 narrower descending limb of the Henle's loop, and then as the 

 somewhat wider ascending limb. The latter again dilates, so 

 as to form the intercalated convoluted tube (Schaltstuck) 

 which ends in a straight collecting tube. These last form the 

 pyramidal processes, and unite finally into single ducts, by 

 repeated junctions with each other at very acute angles. 



The whole system of ducts ma} r often be injected from the 

 ureter. Injections can, however, seldom be carried beyond 

 the loops. The most suitable kidneys for the purpose are 

 those of the pig, dog, or rabbit. The animal must, if possible, 

 be killed by bleeding. A canula, having been secured in the 

 ureter, close to the point at which it leaves the pelvis of the 

 kidney, two per cent, solution of Prussian blue is injected, 

 under a pressure of from 60 to 100 millimeters. The ureter 

 having been ligatured, it is desirable to fill the artery with 

 carmine gelatin. The urinary tubes can be also injected 

 during life by what is called the natural method. A rabbit of 

 moderate size is allowed to lose 10 c. c. of blood from the 

 jugular vein, replacing it with a filtered solution of carmine, 

 containing two drachms of carmine, and one drachm of liquor 

 ammonia* in an ounce of water. If a dog of moderate size 

 is used, 25 c. c. are required. Immediately after the injection, 

 the ureters are ligatured, and the animal is allowed to live for 

 an hour, and then killed. The bloodvessels are then injected 

 with solution of Prussian blue in gelatin, and the organ is 

 placed in common alcohol containing a drop or two of glacial 

 acetic acid. Before placing the kidneys in alcohol, they must 



