42 



PRACTICAL PHrSIOLOGY. 



[V. 



Serum-albumin is completely precipitated from its solution by ammonium 

 sulphate, but not at all by magnesic sulphate. A solution, free from serum- 

 globulin, containing 1-1.5 percent, of salts, coagulates at about 50"^, >vith 5 

 per cent, of NaCl at 75°-8o^ C. 



26. Estimation of Grape-Sugar in Blood. — (a.) Place 20 grams of crystal- 

 lised sodic sulphate in each of three porcelain capsules, and to each add exactly 

 20 grams of the blood to be investigated. Mix the blood and salt together. 

 Boil them until the froth above the clot becomes white, and the clot itself 

 does not present any red specks. Weigh again, and make up the loss by 

 evaporation by the addition of water. The whole is 

 ~ then placed in a small press, and the fluid part ex- 



pressed, collected in a capsule, and afterwards filtered. 

 The filtrate is placed in a burette. 



In a flask place i cc. of Fehling's solution, and to it 

 add a few .-mall pieces of caustic potash and 20 cc. of 

 distilled water. Boil this fluid, and from the burette 

 allow the clear filtrate of the blood to drop into the 

 boiling dilute Fehling's solution until the latter loses 

 every trace of its blue colour (fig. 18). As in all sugar 

 estimations, the process must be repeated several times 

 to get accurate results. Hence the reason why several 

 capsules are prepared. 



Read off, on the burette, the number of cc of the 

 filtrate used, g.gr. =71 cc The formula 



S^ 



8 



in grams the weight of sugar per kilogram of blood. 

 {Bernard.) 



(b.) In Seegen's Method, which may be taken as 

 the type of the newer methods, the proteids are pre- 

 cipitated by ferric acetate. The blood is diluted with 

 8-10 times its volume of water, acidulated with acetic 

 acid, and heated. When the precipitation of proteids 

 commences, render the mixture strongly acid by the 

 addition of acetate of soda and perchloride of iron ; 



then add suflBcient sodic carbonate until the mixture 



vt r _-r V- A ^^ faintly acid, and boil. Allow it to cool, and filter 



StisforESfmatinjftlfe ^^ through a fine cloth filter, free from starch. The 



Sugar in Blood. filtrate ought to be clear. The residue on the 



filter is washed several times with water, and the 



remaining fluid in it expressed by means of a small hand-press. The expressed 



fluid is then mixed with the clear filtrate. If the mixture has a slight reddish 



tint from the admixture of a small quantity of blood-pigment Add a drop 



or two of perchloride of iron to precipitate the last traces of the proteids. 



Filter again. The sugar in the filtrate is estimated in the usual way by 



means of Fehling's solution. 



27. Ash of Hsemoglobln. — Incinerate a small quantity of oxy-hsemoglobin 

 in a platinum capsule. This is done in the manner shown in fig. 19, where 

 the capsule is placed obliquely, and its contents heated in a Bunsen-flame 

 until only the ash remains. The ash is red, and consists of oxide of iron. 



(a.) Dissolve a little in hydrochloric acid ; add })otassic sulphocyanide = a 

 ^ed precipitate, -I- ferrocyanide of potassium = a blue precipitate. 



