HALF-AN-HOUR AT THE MICROSCOPE. Ill 



through the tubes H and I. If there is any obstacle to the 

 escape of the fluids, the pressure in all the vessels will rise and be 

 registered by the height of the mercury in E. To inject, for 

 instance, the kidney of a pig, a cannula made of glass tubing must 

 be fitted securely into the renal artery, and another (same size) 

 into the renal vein. H and I tubes must fit the cannulae well. 

 Heat the masses in B and R to a proper temperature, and keep 

 them so heated until the injection is finished. Special care must 

 be taken with tubes H and I to prevent gelatine passing through 

 being frozen. Now clamp H, and let an assistant turn on a small 

 stream of water until the gelatine begins to flow slowly from I. If 

 the diameter of the cannula is not too small, it may be held with 

 the free end up and filled with gelatine, allowed to drop from 

 the mouth of I. Then slip I over the cannula and unclamp the 

 tube H, and when the gelatine from B begins to flow, slip it over 

 the cannula inserted into the vein. Increase the pressure gradually 

 until as high as experience has taught to be safe for the organ. 

 I have tried this method as recommended on the kidney, the 

 arteries and glomerule being uniformly filled with the red mass, 

 the veins and the system of capillaries surrounding the renal tubes 

 being filled with blue. The lungs and liver are easily well 

 injected. Triple injections of liver are made by first injecting the 

 hepatic artery with a green mass until the whole liver assumes a 

 green tint, and afterwards injecting the portal vein and the hepatic 

 vein with red and blue, as above directed. The same apparatus 

 may be employed for single injections or the double injection 

 described on page io6, by simply clamping one of the tubes C or 

 D. As a matter of course, care must be taken that all the corks 

 fit tighdy in the bottles, otherwise internal pressure may force them 

 out at the very moment when an accident will do most damage. 



1balf*'an*1bour at tbe flDicroscope 



Mftb /I1M% XTutren Mest, f .XS., 3f.1R./lD.S., etc. 



Parasite of Gull, Docophorus Platygaster.— The limbs of 

 the insect require careful study, the head with the mouth 

 organs, etc., and especially the wavy markings of the integument 



