v.] THE BLOOD. 4 1 



The blood is licated with 6 to 8 times its volume of water, and slightly 

 acidulated. The filtrate is evaporated to a small bulk. When a drop of the 

 concentrated filtrate is placed on a slide, cubes of common salt separate out. 



To the colourless filtrate of 23 



(a.) Add silver nitrate = white curdy precipitate soluble in 

 ammonia, but insoluble in nitric acid = cJiloride-^. 



{!).) Add barium chloride = white, heavy precipitate insoluble in 

 nitric acid = sulphates. 



(c.) Add nitric acid and molybdate of ammonium and heat = 

 yellow ^iQoi'^ii^iQ ^ phosphates. 



(rZ.) Test with Fehling's solution or CuSO^ and NaHO and boil 

 = red cuprous oxide = reducing sugai\ which is glucose. 



ADDITIONAL EXEKCTSES. 



24. To Obtain Clear Sernm. —The best way to obtain this is by means of a 

 centrifugal apparatus ; but il the serum contain blood-corpuscles, a fairly 

 clear fluid may be obtained by placing it in a vessel like 

 (fig. 17). It consists of the separated top ot a wide flask 

 provided with a cork in the neck, and in the cork is an 

 adjustable tube provided with a clip. When the serum 

 is placed in the apparatus, it must be aViove the level 

 of the tube. On opening the clip, the clear serum can be 

 drawn oil without di.sturbing the deposit. 



25. Preparation of Serum - Albumin and Serum- 

 Globnlin.- Dilute clear serum with three volumes of a ^'JJ,^ obt^i,iing*cnea? 

 saturated solution of neutral ammonium sulphate, and Seruni. 



add crystals of the same salt to complete saturation. 

 Filter. The deposit contains the two above-mentioned substances, and is 

 washed with a saturated solution of (NHj^^SO^. The deposit is then dis- 

 solved in the smallest possible amount of water and dialysed in a ])archment 

 tube. In j)roportion as the salt dialyses, the serum-globulin is deposited as a 

 white powder in the dialysirig tube, whilst the seruni -albumin remains in 

 solution. It is not difiicult to devise an a])})aratus whereby the water is 

 kept flowing, and even the dialysis tui)e kept in motion in the running water, 

 provided one has some motor power at hand. (S. Lea, Journal of Fhysiology , 

 xi. p. 226). 



After complete dialysis the fluid is filtered, the deposited serum -globulin is 

 collected and washed. The filtrate— which contains the serum-albumin — is 

 carefully neutralised with ammonia, again dialysed, filtered and concentrated 

 at 40" C. After it is cold, the serum-albumin is ])recipitated at once by strong 

 alcohol, expressed, washed with ether and alcohol, and dried. 



