158 The Microscope. 



inch into the aorta ; if, as is usually the case, the aorta be hidden by- 

 adipose tissue, do not cut, but shove the fat aside, and do not forget 

 that passing the nozzle too far up will put it through the arch of 

 the aorta and spoil the job. Having the nozzle in place we will 

 pass the curved needle around the aorta, being careful not to wound 

 the aorta, nor to pass the needle so deeply as to include the superior 

 vena cava. Using a surgeon's knot tie the aorta tightly to the 

 syringe nozzle, then bring the ends of the thread up over the hook 

 at the base of the nozzle and tie it there also to prevent the nozzle 

 from slipping out, then pliice the animal in the warm water and see 

 that the heart is under the water. 



We will now remove the syringe from the warm water and fill 

 it with the warm injecting fluid, place its nose under the water and 

 into the nozzle, giving it a firm twist to secure it. Proceed with 

 the injecting very slowly, taking about a minute to empty the 

 syringe ; you will see the intestinal arteries filling, which will cause 

 a curioiTs vermicular movement of the intestines, the animal will 

 usually kick and go through various motions, although quite dead, 

 while the warm gelatine is filling the system. 



Before the syringe is entirely empty, turn the stop cock, 

 remove and refill the syringe ; in replacing the nose into the nozzle, 

 keep the point under water as before, to prevent the entrance of 

 air. When sufficiently injected, the pads of feet, nose, etc., will 

 be of a natural color. I have had the best results when I passed 

 in the gelatine until considerable of it had made the circuit of the 

 animal and escaped into the water. We having satisfied ourselves 

 that sufiicient fluid has been forced in, will turn the stop cock, 

 remove the syringe and drop the animal into the ice water, where it 

 should remain with the syringe nozzle in the heart for some hours. 



I usually inject the animal in the evening, leave it in the cold 

 water until next morning, when I remove the intestines, cutting 

 them from the stomach, tie the nose of the syringe into the end cut 

 from the stomach, place the intestines into a basin of cold water and 

 inject cold water through them until the water comes out clear. 



I secure the brain by severing the head from the body then 

 holding it in the left hand against a bench, with a screw driver held 

 in right hand, commence at the foramen magnum, break away the 

 skull piece by piece by pressing outward, then by careful manipula- 

 tion cut away the under attachments until the brain drops out. It 

 is best not to divide the brain until it has been in alcohol some 

 hours, after which we will sever the cerebellum from the cerebnim,. 

 but will leave the medulla oblongata, attached to the cerebellum. 



