1894.] MICROSCOPICAL JOURNAL 163 



fluid down, after ligaturing the aorta below the renal 

 artery. This will force the fluid into the arterial sys- 

 tem and around and out by the way of veins. Material 

 which is to be hardened for sections of the cells should 

 be cut with a very sharp blade, from a kidney taken 

 from a very recently killed animal. The pieces should 

 be cut in the form of wedges not more than a quarter to 

 half an inch thick at the base. These should be hardened 

 in an abundance of the hardening reagent. Sections 

 should be extremely thin ; as the tubules are not much 

 more than a thousandth of an inch in diameter, it is ob- 

 vious that the sections will not reveal their interior lu- 

 men, if they are more than that thickness. 



The first thing to do is to "orient" the section, that 

 is to say, to determine its position in the organ from 

 which it came. Very often a student will neglect to 

 orient his section in the beginning, and thus will ob- 

 scure all his subsequent work. It is possible to keep 

 memoranda of the position of the piece, if you cut your 

 own section, from the time it comes out of the organ 

 until the time it is mounted on the slide. In the case of 

 the sections made by students of embryology this must 

 be done or the future determination of the structure of 

 the animal, or part of an animal, is rendered dubious to 

 a certain degree. If this has not been done in the case 

 of the kidney, reference to a description of the organ 

 will enable you to place the section in its proper posi- 

 tion. Figure 1 is drawn for this end. It shows dia- 

 grammatically the pelvis of the kidney, (1), around that 

 the " malpighian pyramids " (2), and around them the 

 " cortex " (3), the whole covered with the " capsule " (4). 

 The dotted line in figure 1 shows the location of figure 2 

 which is a low power view also somewhat diagrammatic 

 of the cortex and part of the malpighian pyramid. The 

 remaining high power views are from the cortical por- 

 tion of the organ which is alike in all parts. 



