ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 



907 



riglit angles. With these are connected the rubber tubes H and I. 

 When water is allowed to flow into the reservoir mentioned above, 

 the air is forced out through A into F, and thence along the tubes D 

 and C into B and E. As soon as the pressure in these bottles becomes 

 sufficiently great, the liquids which they contain will be driven out 



Fig. 218. 



through the tubes H and L. If there should be any obstacle to the 

 escape of these fluid masses, the pressure in all the vessels will rise 

 and be registered by the height of the mercury in E. 



If now it is desired to inject, for instance, the kidney of a pig, a 

 canula made of a glass tube must be fitted securely into the renal 

 artery, and a similar one into the renal vein. The canulse must be 

 of such a size that the rubber tubes H and I will fit them well. Heat 

 the gelatin-masses in the bottles B and R to the proper temperature, 

 and keep them so heated until the injection has been finished. Special 

 care must be taken with the tubes H and I, to prevent the gelatin 

 passing through them from becoming frozen. Having clamped the 

 tube H, have an assistant turn on a small stream of water until the 

 gelatin begins to flow slowly from I. If the diameter of the canula is 

 not too small it may be held with the free end directed upward and 

 filled with gelatin allowed to drop from the mouth of I. Then slip I 

 over the canula. Unclamp the tube H, and when the gelatin from B 

 has begun to flow, slip it over the canula inserted in the vein. Then 

 increase the pressure gradually until it has reached as high a point 

 as experience has taught to be safe for the organ operated on. 



By this apparatus double injections may easily be made of any 

 organs whose veins are not provided with valves. Triple injections 

 of the liver may be made by first injecting the hepatic artery with a 

 green mass until the wliole liver assumes a green tint, and afterwards 

 injecting the portal vein and the hepatic vein with red and blue as 

 above directed. 



