1888.] MICROSCOPICAL JOUEISTAL. 41 



few feet of rubber and glass tubing, and a couple of spring clamps for clos- 

 ing the tubing, when it is necessary to stop the flow. The whole apparatus, 

 when put together, to be as shown in the figure. With good atomizer bulbs 

 I have had no difficulty in maintaining a pressure of lOO millimeters while 

 injecting. 



The injecting canula, for fastening in the blood-vessel, can be made from 

 a small glass tube, by heating it over an alcohol lamp, and drawing it out so 

 that it will be decreased in size just back of the point. This will prevent its 

 slipping out of the blood-vessel when tied in. It is better, however, to have 

 brass canula and stop-cocks, such as are furnished with Beck's injecting 

 syringe, and which m.ay be bought of any dealer in microscopical goods. 



Before making an injection the apparatus should always be arranged, and 

 then tested by closing -the exit tube and gradually raising the pressure to loo 

 millimeters, so that any defects or leaks may be found and remedied before 

 the injection is begun. Before killing the animal the box is filled below the 

 shelf with water at 40° C, and a lamp placed underneath to keep the temper- 

 ature at that point. The melted injecting mass is then poured into the in- 

 jecting bottle, in order that it may attain the same temperature. About 13 

 ounces of a £ per cent, salt solution is poured into another bottle, also ar- 

 ranged with injection tubes and placed in the box. The animal is chloro- 

 formed and, before the action of the heart ceases, a window is cut in the 

 thorax, the pericardium opened, the heart drawn out with a tenaculum, and 

 its apex cut ofl'. The escape of the blood is aided by holding the animal 

 up, first by the head and then by the tail. As soon as the blood ceases to 

 flow a canula is passed through the left ventricle into the aorta and fastened in 

 bv a ligature passed around the artery. -The animal is then placed in the 

 box, the canula connected with the delivery tube of the bottle containing the 

 salt solution having first forced the solution through the tube until all air is 

 displaced, the box covered with the glass, and the solution injected at a pres- 

 sure of 50 millimeters, until it escapes clear from the right side of the heart. 



The canula is now disconnected from the bottle of salt solution and con- 

 nected with that containing the carmine fluid. Beginning the injection with 

 a pressure of 50 ra.m., this is gradually increased to 100 m.m., but no more. 

 After a time, the veins entering the right auricle may be tied and the injec- 

 tion continued until the eyes, tongue, ears, and feet show by their color that 

 the capillaries are filled. The aorta is then ligated, and the animal placed in 

 ice water, or a refrigerator, to remain until cold, when the parts desired are 

 to be removed and hardened in alcohol. This method will, of course, not 

 inject the lungs. They must be injected through the pulmonary artery, and 

 then distended by injecting the air passages with alcohol through the trachea. 



Studies for beginners. — I. 



By H. L. OSBORN. 



THE YEAST PLANT. 



The winter weather need not deter us from using the microscope. It is 

 therefore proposed to narrate a few easy and yet interesting studies which 

 may now be prosecuted. To be sure the ponds are frozen and smaller forms 

 of life have sought seclusion or been overtaken by death. But they have left 

 traces behind them and can be hunted out, revived, and made to reveal many 

 secrets. The yeast plant shall serve this purpose first. 



How many persons know that yeast is a plant? It is a very small one, 



