180 Dr. S. J. Lewis. Ultra-Violet Absorption Spectra and 



following may be mentioned. It was found desirable to employ fairly large 

 quantities of material, such as two litres, of the clear serum and at each stage 

 to work at first with solutions of ammonium sulphate, which were as precisely 

 as possible of full, one-half or one-third saturation, and then, when required, 

 to add small but known excesses. The albumin precipitates were dissolved in 

 such a quantity of water as to produce a 14 or 16 per cent, solution, and 

 reprecipitated, the first time by the addition of specially recrystallised 

 ammonium sulphate, and on subsequent occasions by the aid of ammonium 

 sulphate and a veiy small quantity of acetic acid, and left to stand over for 

 some days to allow the precipitate to become micro-crystalline. With horse 

 serum the best crystals were obtained after the fourth precipitation. With 

 human serum, the particles did not form cystals, but they exhibited a well- 

 defined uniformity of shape, suggestive of an approach to a radiate crystalline 

 structure. 



The mixed globulins were precipitated three times, and then separated from 

 one another by dissolving in sufficient water to produce an approximately 

 2 per cent, solution, and precipitating by increasing the ammonium sulphate 

 concentration to one-third saturation. 



The pseudo-globulin was freed from accompanying eu-globulin by slightly 

 increasing the ammonium sulphate to nearly 36 per cent, saturation and 

 filtering, and then by adding four small equal quantities of saturated 

 ammonium sulphate solution, and allowing to stand after each addition, so 

 that the final concentration was nearly but not quite 37 per cent, saturated, 

 with a view to removing any remaining eu-globulin. After filtration, the 

 pseudo-globulin was reprecipitated by increasing the ammonium sulphate to 

 one-half saturation, and collected for use. 



The eu-globulin was reprecipitated by ammonium sulphate four times from 

 dilute solutions. With ascitic fluid, a small amount of a brown jelly-like 

 substance sometimes accompanied the eu-globulin. When this was the case, 

 the impure eu-globulin was dissolved as completely as possible in a small 

 quantity of water and then saturated ammonium sulphate solution was added, 

 until a small but considerable precipitate was formed, stirred well and filtered. 

 The jelly-like substance remained on the filter together with a small quantity 

 (probably 20 or 30 per cent.) of the eu-globulin. The filtrate was then quite 

 clear, and was treated as an ordinary solution of eu-globulin. Subsequent 

 precipitations usually gave no trouble. 



Optical Potation of the Proteins. 



It was at first assumed that each protein would have a constant rotatory 

 power, and that observations of the specific rotations would settle the question 



