APPENDIX TO CHAPTER XIII. H9 



glass, and in half an hour examine again. The blood will then have 

 separated into a tiny red clot, lying in nearly colorless serum. 



5. If a slaughter house is accessible, the clotting of blood may be 

 still better illustrated. Provide two large wide-necked glass bottles 

 and a bundle of twigs. When the butcher bleeds an animal, collect 

 in one bottle some blood, taking care that nothing else (contents of 

 the stomach, for example, when the animal is bled, as is often done, 

 by cutting is throat) gets mixed with it. Put this bottle aside until 

 the blood clots, and carry it home with the least possible shaking. 

 Next day the mass will exhibit a beautiful clot floating in serum. 

 The latter will probably be tinted red, as the jolting in conveying the 

 specimen from the slaughter-house shakes some of the red corpuscles 

 out of the clot into the serum. 



6. In the other bottle collect blood and stir it vigorously with the 

 twigs for three or four minutes. Next day this specimen will not 

 have clotted, but on the twigs will be found a quantity of stringy 

 elastic material (fibrin), which becomes pure white when thoroughly 

 washed with water. 



7. Take some of the serum from specimen 5. Observe that it 

 does not coagulate spontaneously. Heat it in a test-tube over a 

 spirit-lamp; its albumen will then coagulate, like the white of a hard- 

 boiled egg, and the whole will become solid. 



8. Place a small quantity of whipped blood (6) on a piece of plati- 

 num foil. Heat over a spirit-lamp. After the drop dries it blackens, 

 showing that it contains much animal matter. As the heating is con- 

 tinued this is burnt away, and a white ash, consisting of the mineral 

 constituents of the blood, is left. 



THE CIRCULATORY ORGANS. 



1. In the following directions "dorsal" means the side of the heart 

 naturally turned towards the vertebral column, "ventral" the side 

 next the breast-bone; "right" and "left" refer to the proper right 

 and left of the heart when in its natural position in the body; " an- 

 terior" means more towards the head in the natural position of the 

 parts; and "posterior" the part turned away from the head. 



2. Get your butcher to obtain for you a sheep's heart, not cut out 

 of the bag (pericardium), and still connected with the lungs. Impress 

 upon him that no hole must be punctured in the heart, such as is usu- 

 ally made when a slaughtered sheep is cut up for market. 



3. Place the heart and lungs on their dorsal sides on a table in 

 their natural relative positions, and with the windpipe directed away 

 from you. Note the loose bag (pericardium} in which the heart lies, 

 and the piece of midriff (diaphragm) which usually is found attached 

 to its posterior end. 



4. Carefully dissecting away adherent fat, etc., trace the vessels 

 below named until they enter the pericardium. Be very careful not 

 to cut the veins, which, being thin, collapse when empty, and may 

 be easily overlooked until injured. As each vein is found stuff it 

 with raw cotton, which makes its dissection much easier. 



a. The vena cava inferior: find it on the under (abdominal) side of 

 the diaphragm; thence follow it until it enters the pericardium, about 



