PRACTICAL EXERCISES 689 



hour after death, in a case of tetanus, the temporal urc was found 

 to be 45-3, while before death it was 447 (Wunderlirh). In dogs 

 a slight post-mortem rise may be demonstrated, especially when 

 the body is wrapped up; but when an animal has been long under 

 the influence of anaesthetics no indication whatever of the phenom- 

 enon may be obtained. The explanation of post-mortem rise of 

 temperature is to be found: (i) In the continued metabolism of the 

 tissues for some time after the heart has ceased to beat, for the cell 

 dies harder than the body. (2) In the diminished loss of heat, due 

 to the stoppage of the circulation. (3) To a small extent in physical 

 changes (rigor mortis, coagulation of blood) in which heat is set free. 



PRACTICAL EXERCISES ON CHAPTERS X., XL, AND XII. 



i. Glycogen* (i) Preparation. (a) Cut an oyster into two or three 

 pieces, throw it into boiling water, and boil for a minute or two. Rub 

 up in a mortar with clean sand, and again boil. Filter. Precipitate 

 any proteins which have not been coagulated, by adding alternately 

 a drop or two of hydrochloric acid and a few drops of potassio-mercuric 

 iodide so long as a precipitate is produced. Only a small quantity of 

 these reagents will be required, as the greater part of the proteins has 

 been already coagulated by boiling. Filter if any precipitate has formed. 

 The nitrate is opalescent. Precipitate the glycogen from the nitrate (after 

 concentration on the water-bath if it exceeds a few c.c. in bulk) by the 

 addition of four or five times its volume of alcohol. Filter off the precipi- 

 tate, wash it on the filter with alcohol, and dissolve it in a little water. 

 To some of the solution add a drop or two of iodine ; a reddish-brown 

 (port wine) colour is produced, which disappears on heating, returns on 

 cooling, is removed by an alkali, restored by an acid. Add saliva to some 

 of the glycogen solution, and put in a bath at 40 C. In a few minutes 

 reducing sugar (maltose) will be found in it by Trommer's test (p. 10). 



Note that dextrin (erythrodextrin) gives the same colour with iodine 

 as glycogen does. Dextrin is also precipitated by alcohol, but a 

 greater proportion must be added to cause complete precipitation. 

 Glycogen is completely precipitated by saturation with magnesium 

 sulphate or ammonium sulphate, so that the filtrate no longer gives 

 the reddish colour with iodine. A pure solution of erythrodextrin is 

 not precipitated. On the addition of a drop or two of a solution of 

 basic lead acetate to a solution of glycogen in distilled water, a pre- 

 cipitate forms immediately. When the same reagent is added to a 

 solution of dextrin in distilled water there is no immediate precipitate. 

 Maltose is formed when dextrin is digested with saliva. 



(b) Cut another oyster into pieces, throw it into boiling water acidu- 

 lated with dilute acetic acid, and boil for a few minutes. Rub up in a 

 mortar with sand, boil again, and filter. Test a portion of the fil- 

 trate with iodine for glycogen. Precipitate the rest with alcohol, 

 filter, dissolve the precipitate in water, and test again for glycogen. 

 On boiling some of the opalescent solution for a few minutes after the 

 addition of a few drops of sulphuric acid the opalescence disappears, and 



* For the quantitative estimation of glycogen in organs, Pfluger's method 

 is the best. The organ is minced and heated with strong (Go per cent.) potas- 

 sium hydroxide. The glycogen is precipitated with alcohol, and then, after 

 hvdrolysis with hydrochloric, arid, estimated as dextrose. 



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