AND HOW TO USE IT. 109 



sure-bottle with the manometer and Higginson's syringe, as in the 

 engraving ; also with the mass bottle. The tube of this bottle, 

 which conveys mass mvay from the bottle, is now clamped, and 

 must never for a second get out of the warm water. Having a 

 small basinful of water, squeeze the Higginson's syringe, watching 

 manometer, to raise the mercury half-an-inch. This done, remove 

 the clamp from efflux tube, and the red fluid, after driving out a 

 few air-bubbles, begins to flow out. We at once make the con- 

 nection, and all dangers are passed if we have tied our nozzles 

 properly into the artery and connecting part, and fastened our 

 stoppers thoroughly into our Woulffs bottles. Hold the head of 

 the animal, which should be to the left, with the left hand to 

 watch the pale gums, tongue, eyelids, and vascular parts become 

 suffused with a pale blush, which gradually deepens ; gently 

 squeeze and relax the barrel of syringe, and glance at the mercury 

 from time to time. When it has risen four or at most five inches, 

 the animal will be completely injected. The visible mucous 

 membrane and intestines will be dark red and much swollen. 

 Remove the animal, place in ice-cold water or under the tap for 

 an hour or two, and divide into parts as required. It is best to 

 prepare the injection masses immediately before they are used ; 

 but they can be kept for some time, I find, if chloral be added to 

 the gelatine. Before being used, the mass should be always care- 

 fully filtered through flannel. 



Haye's Method of Double Injections. — Fit a cannula into the 

 aorta of a cat, and inject a gelatine mass coloured with carmine 

 until it is seen flowing from the right side of the heart ; then 

 detach the tube conveying the red mass ; slip one containing a 

 blue gelatine mass over the same cannula, and apply the pressure 

 again. Into this blue mass is mixed thoroughly a quantity of 

 starch — preferably from wheat. This starch-mass pushes the 

 carmine mass before it until the starch-grains enter the capillaries 

 and effectually plug them up. The arteries are left blue and veins 

 red. The first mass injected need not be unusually thin. The 

 capacity of the capillaries is so great, compared with that of the 

 arteries, that any commingling of the two colours is concealed in 

 them. Carmine is used for the veins because of the ease with 

 which it is prepared, its permanence, and the facility with which 



