I.] 



THE PROTEIDS. 



(d.) For the effect of a dilute acid and pepsin (see " Digestion"). These 

 "digest" fibrin, and convert it into proteose, and ultimately into peptone. 



(e.) It decomposes hydric peroxide, and turns freshly-prepared tincture of 

 guaiacum blue (see " Blood "). 



(/.) Digest fibrin in 10 per cent, sodium chloride for two days. A small 

 part is dissolved ; boil the fluid = coagulation. 



(ii.) MYOSIN (see "Muscle"), 

 (iii.) CASEIN (see "Milk"), 

 (iv.) GLUTEN (see "Bread"). 



12. VIII. Lardacein, or Amyloid Substance. This occurs in organs, e.g., 

 liver and kidney, undergoing the pathological degeneration known as amyloid', 

 waxy or wax like, or albumenoid disease. It is insoluble in dilute acids or 

 alkalies, and it is not acted on by the gastric juice. It gives several distinct 

 reactions, not stains, with certain staining fluids. 



(a. ) A solution of iodine in iodide of potassium gives a deep brown or 

 mahogany stain when poured on a section of a fresh waxy organ. 



(b.) With iodine and sulphuric acid occasionally a blue reaction is obtained. 



(c.) Methyl-violet and gentian-violet give a rose-pink reaction with the 

 waxy parts, while others, i.e., the healthy parts of an organ, give different 

 shades of blue or purple. 



FlO. 2. Apparatus of Halliburton for Fractional Heat Coagulation of Proteids. T. Tap 

 for Water ; C. Copper vessel with spiral tube ; a. Inlet, and b. Outlet-tube to the 

 flask ; t. Test tube, with fluid and thermometer. 



13. Fractional Heat Coagulation, e.g., of blood-serum. The serum or 

 other fluid containing proteid is heated until a flocculent precipitate occurs. 

 Filter. The filtrate is again heated to a higher temperature, until a similar 

 precipitate app-ars. This precipitate is filtered off, and the above process 

 repeated, until the liquid is free of proteid. 



The arrangements shown in fig. i may be used, but the rise of temperature 

 takes place rather too slowly, and it is difficult to maintain the temperature 

 constant for a considerable length of time when one is investigating a large 

 number of fluids. The following apparatus used by Halliburton (fig. 2) is 

 more convenient. "A glass flask supported on a stand ; down its neck is 

 placed a test-tube, in-which again is placed the liquid under investigation in 

 sufficient quantity to cover the bulb of a thermometer placed in it. The^as^k 

 is kept filled with hot water, and this water is constantly flowing. it 

 enters by (a), passing to the bottom of the flask, and leaves at (b). Ine 



